Support material formulation and additive manufacturing processes employing same

ABSTRACT

Novel support material formulations, characterized as providing a cured support material with improved dissolution rate, while maintaining sufficient mechanical strength, are disclosed. The formulations comprise a water-miscible non-curable polymer, a first water-miscible, curable material and a second, water-miscible material that is selected capable of interfering with intermolecular interactions between polymeric chains formed upon exposing the first water-miscible material to curing energy. Methods of fabricating a three-dimensional object, and a three-dimensional object fabricated thereby are also disclosed.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/752,621 filed on Feb. 14, 2018, which is a National Phase of PCTPatent Application No. PCT/IL2016/050886 having International FilingDate of Aug. 14, 2016, which claims the benefit of priority under 35 USC§ 119(e) of U.S. Provisional Patent Application Nos. 62/205,010 and62/205,009, both filed on Aug. 14, 2015. The contents of the aboveapplications are all incorporated by reference as if fully set forthherein in their entirety.

FIELD AND BACKGROUND OF THE INVENTION

The present invention, in some embodiments thereof, relates to additivemanufacturing (AM), and more particularly, but not exclusively, toformulations useful for forming a support material in additivemanufacturing such as three-dimensional inkjet printing, and to methodsof additive manufacturing utilizing same.

Additive manufacturing (AM) is a technology enabling fabrication ofarbitrarily shaped structures directly from computer data via additiveformation steps (additive manufacturing; AM). The basic operation of anyAM system consists of slicing a three-dimensional computer model intothin cross sections, translating the result into two-dimensionalposition data and feeding the data to control equipment which fabricatesa three-dimensional structure in a layerwise manner.

Additive manufacturing entails many different approaches to the methodof fabrication, including three-dimensional printing such as 3D inkjetprinting, electron beam melting, stereolithography, selective lasersintering, laminated object manufacturing, fused deposition modeling andothers.

Three-dimensional (3D) printing processes, for example, 3D inkjetprinting, are being performed by a layer by layer inkjet deposition ofbuilding materials. Thus, a building material is dispensed from adispensing head having a set of nozzles to deposit layers on asupporting structure. Depending on the building material, the layers maythen be cured or solidified using a suitable device.

Various three-dimensional printing techniques exist and are disclosedin, e.g., U.S. Pat. Nos. 6,259,962, 6,569,373, 6,658,314, 6,850,334,6,863,859, 7,183,335, 7,209,797, 7,225,045, 7,300,619, and 7,500,846 andU.S. patent application having Publication No. 20130073068, all by thesame Assignee.

During the additive manufacturing (AM) process, the building materialmay include “model material” (also known as “object material” or“modeling material”), which is deposited to produce the desired object,and frequently, another material (“support material” or “supportingmaterial”) is used to provide temporary support to the object as it isbeing built. The other material is referred to herein and in the art as“support material” or “supporting material”, and is used to supportspecific areas of the object during building and for assuring adequatevertical placement of subsequent object layers. For example, in caseswhere objects include overhanging features or shapes, e.g. curvedgeometries, negative angles, voids, and the like, objects are typicallyconstructed using adjacent support constructions, which are used duringthe printing and then subsequently removed in order to reveal the finalshape of the fabricated object.

The modeling material and the supporting material may be initiallyliquid and subsequently hardened to form the required layer shape. Thehardening process may be performed by a variety of methods, such as UVcuring, phase change, crystallization, drying, etc. In all cases, thesupport material is deposited in proximity of the modeling material,enabling the formation of complex object geometries and filling ofobject voids. In such cases, the removal of the hardened supportmaterial is liable to be difficult and time consuming, and may damagethe formed object.

When using currently available commercial print heads, such as ink-jetprinting heads, the support material should have a relatively lowviscosity (about 10-20 cPs) at the working, i.e., jetting, temperature,such that it can be jetted. Further, the support material should hardenrapidly in order to allow building of subsequent layers. Additionally,the hardened support material should have sufficient mechanical strengthfor holding the model material in place, and low distortion for avoidinggeometrical defects.

Examples of materials that can be used as supporting materials are phasechange materials, with wax being a non-limiting example. At anappropriately high temperature these materials melt and thus permitsupport removal when in the liquid state. One of the drawbacks of suchphase change is that the temperature required for melting the supportingmaterial may also cause deformation of the model, and hence of theobject structure.

Known methods for removal of support materials include mechanical impact(applied by a tool or water-jet), as well as chemical methods, such asdissolution in a solvent, with or without heating. The mechanicalmethods are labor intensive and are often unsuited for small intricateparts.

For dissolving the support materials, the fabricated object is oftenimmersed in water or in a solvent that is capable of dissolving thesupport materials. The solutions utilized for dissolving the supportmaterial are also referred to herein and in the art as “cleaningsolutions”. In many cases, however, the support removal process mayinvolve hazardous materials, manual labor and/or special equipmentrequiring trained personnel, protective clothing and expensive wastedisposal. In addition, the dissolution process is usually limited bydiffusion kinetics and may require very long periods of time, especiallywhen the support constructions are large and bulky. Furthermore,post-processing may be necessary to remove traces of a ‘mix layer’ onobject surfaces. The term “mix layer” refers to a residual layer ofmixed hardened model and support materials formed at the interfacebetween the two materials on the surfaces of the object beingfabricated, by model and support materials mixing into each other at theinterface between them.

Additionally, methods requiring high temperatures during support removalmay be problematic since there are model materials that aretemperature-sensitive, such as waxes and certain flexible materials.Both mechanical and dissolution methods for removal of support materialsare especially problematic for use in an office environment, whereease-of-use, cleanliness and environmental safety are majorconsiderations.

Water-soluble materials for 3D building have been previously described.For example, U.S. Pat. No. 6,228,923 describes a water solublethermoplastic polymer—Poly(2-ethyl-2-oxazoline)—for use as a supportmaterial in a 3D building process involving high pressure and hightemperature extrusion of ribbons of selected materials onto a plate.

A water-containing support material comprising a fusible crystal hydrateis described in U.S. Pat. No. 7,255,825. Fusible crystal hydratesundergo a phase change from solid to liquid (i.e. melt) usually athigher than ambient temperature (typically between 20° C. and 120° C.depending upon the substance). Typically, upon melting, fusible crystalhydrates turn into aqueous solutions of the salts from which they areformed. The water content in these solutions is typically high enough tomake the solutions suitable for jetting from a thermal ink-jetprinthead. The melting process is reversible and material dispensed in aliquid state readily solidifies upon cooling.

Compositions suitable for support in building a 3D object are described,for example, in U.S. Pat. Nos. 7,479,510, 7,183,335 and 6,569,373, allto the present Assignee. Generally, the compositions disclosed in thesepatents comprise at least one UV curable (reactive) component, e.g., anacrylic component, at least one non-UV curable component, e.g. a polyolor glycol component, and a photoinitiator. After irradiation, thesecompositions provide a semi-solid or gel-like material capable ofdissolving or swelling upon exposure to water, to an alkaline or acidicsolution or to a water detergent solution. 3D printing methodologiesusing such a soluble support material are also known as “Soluble SupportTechnology” or SST, and the support material formulation is oftenreferred to a “soluble support material” or “soluble support materialformulation”. Soluble support materials should beneficially featuresufficient water solubility, so as to be removed during a relativelyshort time period, or sufficient solubility in a non-hazardous cleaningsolution, yet, at the same, to exhibit mechanical properties sufficientto support the printed object during the additive manufacturing process.

Besides swelling, another characteristic of such a support material maybe the ability to break down during exposure to water, to an alkaline oracidic solution or to a water detergent solution because the supportmaterial is made of hydrophilic components. During the swelling process,internal forces cause fractures and breakdown of the cured support. Inaddition, the support material can contain a substance that liberatesbubbles upon exposure to water, e.g. sodium bicarbonate, whichtransforms into CO₂ when in contact with an acidic solution. The bubblesaid in the process of removal of support from the model.

Additional Background art includes U.S. patent application havingPublication No. 2003/0207959.

SUMMARY OF THE INVENTION

There is an unmet need for improved support materials in 3D inkjetprinting.

The present inventors have now designed and successfully practiced novelsoluble support material formulations, which supersede currently knownsupport material formulations. The hardened (e.g., cured) supportmaterial obtained upon dispensing and curing these formulations caneasily and efficiently be removed by contacting an alkaline solution,with reduced dissolution time and increased dissolution rate, while notcompromising the mechanical properties of the support material.

The support material formulations described herein include, in additionto curable (reactive) components, and polymeric non-curable components,as described herein, also a curable component that reduces a degree ofcross-linking in the cured support material, or otherwise interfereswith intermolecular interactions between the cured polymeric componentsformed upon curing a support material formulation. The additionalcurable component attributes to decreased dissolution time of the curedsupport material, without compromising the mechanical properties of thesupport material.

According to an aspect of some embodiments of the present inventionthere is provided a support material formulation comprising:

a non-curable water-miscible polymer;

a first water-miscible, curable material; and

at least one second water-miscible curable material,

wherein the second curable material is selected capable of interferingwith intermolecular interactions between polymeric chains formed uponexposing the first water-miscible material to curing energy.

According to some of any of the embodiments described herein, the secondcurable material is selected capable of forming hydrogen bonds with thepolymeric chains formed upon exposing the first water-soluble materialto the curing energy.

According to some of any of the embodiments described herein, the firstcurable material comprises a mixture of a mono-functional curablematerial and a multi-functional (e.g., di-functional) curable material.

According to some of any of the embodiments described herein, the secondcurable material is capable of interfering with a chemical cross-linkingbetween the polymeric chains, the chemical cross-linking being impartedby the multi-functional (e.g., di-functional) curable material.

According to some of any of the embodiments described herein, the secondcurable material is capable of reducing a degree of a chemicalcross-linking between the polymeric chains, the chemical cross-linkingbeing imparted by the multi-functional (e.g., di-functional) curablematerial.

According to some of any of the embodiments described herein, the secondcurable material is capable of forming hydrogen bonds with the polymericchains.

According to some of any of the embodiments described herein, the secondcurable material features at least two hydrogen bond-forming chemicalmoieties.

According to some of any of the embodiments described herein, each ofthe at least two hydrogen bond-forming chemical moieties independentlycomprises at least one atom selected from oxygen and nitrogen.

According to some of any of the embodiments described herein, each ofthe at least two hydrogen bond-forming chemical moieties isindependently selected from amide, carboxylate, hydroxy, alkoxy,aryloxy, ether, amine, carbamate, hydrazine, a nitrogen-containingheteralicyclic, and an oxygen-containing heteralicyclic.

According to some of any of the embodiments described herein, at leasttwo of the hydrogen bond-forming chemical moieties are separated by2-10, or by 2-8, or by 2-6 atoms (e.g., carbon atoms).

According to some of any of the embodiments described herein, each ofthe first and second curable materials is a UV-curable material.

According to some of any of the embodiments described herein, each ofthe first and second curable materials independently comprises anacrylate, a methacrylate, an acrylamide or a methacrylamide curablemoiety.

According to some of any of the embodiments described herein, the firstcurable material comprises a poly(alkylene glycol) acrylate.

According to some of any of the embodiments described herein, the firstcurable material comprises a mono-functional poly(alkylene glycol)acrylate.

According to some of any of the embodiments described herein, the firstcurable material comprises a mixture of a mono-functional poly(alkyleneglycol) acrylate and a multi-functional, e.g., di-functional,poly(alkylene glycol) acrylate.

According to some of any of the embodiments described herein, the firstcurable material comprises a mixture of a poly(alkylene glycol) acrylateand a poly(alkylene glycol) diacrylate.

According to some of any of the embodiments described herein, a weightratio between the mono-functional poly(alkylene glycol) acrylate and themulti-functional (e.g., di-functional) poly(alkylene glycol) acrylate(e.g., poly(alkylene glycol) diacrylate) in the first curable materialranges from 70:30 to 95:5.

According to some of any of the embodiments described herein, the secondcurable material is selected from an acrylate, a methacrylate, anacrylamide or a methacrylamide.

According to some of any of the embodiments described herein, the secondcurable material is represented by Formula I:

wherein:

Ra is selected from H, C(1-4) alkyl and a hydrophilic group;

k is an integer ranging from 2 to 10, or from 2 to 8, or from 2 to 6, orfrom 2 to 4, or is 2 or 3; and

X and Y are each independently a hydrogen bond-forming moiety thatcomprises at least one nitrogen and/or oxygen atom.

According to some of any of the embodiments described herein, Y isselected from hydroxyl, alkoxy, aryloxy, amine, alkylamine,dialkylamine, carboxylate, hydrazine, carbamate, hydrazine, anitrogen-containing heteralicyclic, and an oxygen-containingheteralicyclic.

According to some of any of the embodiments described herein, X is —O—.

According to some of any of the embodiments described herein, Ra is H,such that the second curable material is an acrylate.

According to some of any of the embodiments described herein, X is—NRc-, wherein Rc is hydrogen, alkyl, cycloalkyl or aryl.

According to some of any of the embodiments described herein, Ra is H,such that the second curable material is an acrylamide.

According to some of any of the embodiments described herein, the secondcurable material is an acrylamide substituted by at least one hydrogenbon-forming chemical moiety.

According to some of any of the embodiments described herein, theacrylamide is substituted by a chemical moiety selected fromhydroxyalkyl, alkoxyalkyl, aminoalkyl, alkylaminoalkyl,dialkylaminoalkyl, carboxyalkyl, hidrazinoalkyl, carbamoylalkyl, and analkyl substituted by any other hydrogen bond-forming chemical moiety asdescribed herein.

According to some of any of the embodiments described herein, aconcentration of the second curable material ranges from 5% to 40% byweight of the total weight of the formulation.

According to some of any of the embodiments described herein, aconcentration of the first curable material ranges from 5 to 40, or from5 to 30, or from 5 to 25, or from 5 to 20, or from 10 to 20, or from 5to 15, or from 10 to 15, weight percents of the total weight of theformulation.

According to some of any of the embodiments described herein, aconcentration of the first curable material is lower than 30%, or lowerthan 25%, or lower than 20%, or lower than 15% by weight of the totalweight of the formulation.

According to some of any of the embodiments described herein, aconcentration of the second curable monomer ranges from 1 to 40, or from1 to 30, or from 1 to 20, or from 5 to 20, or from 5 to 15, or from 5 to10, weight percents of the total weight of the formulation.

According to some of any of the embodiments described herein, thewater-miscible polymer comprises a polyol.

According to some of any of the embodiments described herein, the polyolis selected from the group consisting of Polyol 3165, polypropyleneglycol, and polyglycerol.

According to some of any of the embodiments described herein, aconcentration of the water-miscible polymer ranges from 30% to 80% byweight of the total weight of the formulation.

According to some of any of the embodiments described herein, theformulation further comprises an initiator, and optionally an additionalagent, such as a surface active agent and/or an inhibitor and/orstabilizer.

According to some of any of the embodiments described herein, a curedsupport material formed upon exposing the formulation to a curing energyis dissolvable in an alkaline solution.

According to some of any of the embodiments described herein, adissolution time of a cured support material when immersed in thealkaline solution is at least 2-folds, or at least 4-folds, shorter thana dissolution time of a cured support material made of a comparablesupport material formulation that is absent the second curable materialas described herein in any of the respective embodiments.

According to some of any of the embodiments described herein, adissolution time of a 16-grams cube made of the cured support materialand immersed in 800 mL of the alkaline solution is less than 10 hours,or less than 5 hours, or less than 2 hours.

According to some of any of the embodiments described herein, thealkaline solution comprises an alkali metal hydroxide.

According to some of any of the embodiments described herein, thealkaline solution further comprises an alkali metal silicate.

According to some of any of the embodiments described herein, a 20 mm×20mm×20 mm object made of (e.g., printed by inkjet printing, or preparedin a mold) the support material formulation and formed upon exposing theformulation to a curing energy is characterized by a mechanical strengthof at least 100 N.

According to some of any of the embodiments described herein, a curedsupport material formed upon exposing the formulation to a curing energyis characterized by a mechanical strength that is lower than amechanical strength of a cured support material made of a comparablesupport material formulation that is absent the second curable materialand comprises substantially the same total concentration of curablematerials as the formulation, by no more than 50% or by no more than40%, or by no more than 30%.

According to an aspect of some embodiments of the present inventionthere is provided a method of fabricating a three-dimensional modelobject, the method comprising dispensing a building material so as tosequentially form a plurality of layers in a configured patterncorresponding to the shape of the object, wherein the building materialcomprises a modeling material formulation and a support materialformulation, and wherein the support material formulation comprises theformulation as described herein in any of the respective embodiments.

According to some of any of the embodiments described herein, the methodfurther comprises, subsequent to the dispensing, exposing the buildingmaterial to curing energy, to thereby obtain a printed objectedcomprised of a cured modeling material and a cured support material.

According to some of any of the embodiments described herein, the methodfurther comprises removing the cured support material, to thereby obtainthe three-dimensional model object.

According to some of any of the embodiments described herein, theremoving comprises contacting the cured support material with a cleaningsolution, for example, an alkaline solution.

According to some of any of the embodiments described herein, thecleaning solution comprises an alkali metal hydroxide.

According to some of any of the embodiments described herein, thecleaning solution further comprises an alkali metal silicate.

According to an aspect of some embodiments of the present inventionthere is provided a three-dimensional object fabricated by the method asdescribed herein.

Unless otherwise defined, all technical and/or scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which the invention pertains. Although methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of embodiments of the invention, exemplarymethods and/or materials are described below. In case of conflict, thepatent specification, including definitions, will control. In addition,the materials, methods, and examples are illustrative only and are notintended to be necessarily limiting.

Implementation of the method and/or system of embodiments of theinvention can involve performing or completing selected tasks manually,automatically, or a combination thereof. Moreover, according to actualinstrumentation and equipment of embodiments of the method and/or systemof the invention, several selected tasks could be implemented byhardware, by software or by firmware or by a combination thereof usingan operating system.

For example, hardware for performing selected tasks according toembodiments of the invention could be implemented as a chip or acircuit. As software, selected tasks according to embodiments of theinvention could be implemented as a plurality of software instructionsbeing executed by a computer using any suitable operating system. In anexemplary embodiment of the invention, one or more tasks according toexemplary embodiments of method and/or system as described herein areperformed by a data processor, such as a computing platform forexecuting a plurality of instructions. Optionally, the data processorincludes a volatile memory for storing instructions and/or data and/or anon-volatile storage, for example, a magnetic hard-disk and/or removablemedia, for storing instructions and/or data. Optionally, a networkconnection is provided as well. A display and/or a user input devicesuch as a keyboard or mouse are optionally provided as well.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the invention are herein described, by way ofexample only, with reference to the accompanying drawings. With specificreference now to the drawings in detail, it is stressed that theparticulars shown are by way of example and for purposes of illustrativediscussion of embodiments of the invention. In this regard, thedescription taken with the drawings makes apparent to those skilled inthe art how embodiments of the invention may be practiced.

In the drawings:

FIG. 1 is a bar graph presenting the dissolution time, in an exemplaryalkaline solution as described herein, of a printed 16-grams cube formedof a support material formulation comprising an exemplary first curablematerial as described herein, as a function of the concentration of thefirst curable material (dashed bars) and of the same cube formed of asupport material formulation in which 10% of an exemplary second curablematerial (HAA) were added to the first curable material (black bar);

FIG. 2 is a bar graph presenting the mechanical strength measured for aprinted 16-grams cube formed of a support material formulationcomprising an exemplary first curable material as described herein, as afunction of the concentration of the first curable material (dashedbars) and of the same cube formed of a support material formulation inwhich 10% of an exemplary second curable material (HAA) were added tothe first curable material (black bar);

FIG. 3 is a bar graph presenting the dissolution time, in an exemplaryalkaline solution as described herein, of various model objects formedwith a support material formulation comprising an exemplary firstcurable material as described herein, as a function of the concentrationof the first curable material and of the same cube formed of a supportmaterial formulation in which various concentrations of an exemplarysecond curable material (HAA) were added to the first curable material(the shape of the model objects shown in the insets);

FIG. 4 is a bar graph presenting the mechanical strength measured for aprinted 16-grams cube formed of a support material formulationcomprising an exemplary first curable material as described herein, as afunction of the concentration of the first curable material (dashedbars), of the same cube formed of a support material formulation inwhich 10% of an exemplary second curable material (HAA) were added tothe first curable material (black bar), and of the same cube formed of asupport material formulation in which a mixture of 5% of an exemplarysecond curable material (HAA) and 5% of another exemplary second curablematerial was added to the first curable material (blank bar);

FIG. 5 is a bar graph presenting the mechanical strength measured for aprinted 16-grams cube formed of a support material formulationcomprising an exemplary first curable material as described herein, as afunction of the concentration of the first curable material (dashedbars), of the same cube formed of a support material formulation inwhich 10% of an exemplary second curable material (HAA) were added tothe first curable material (black bar), and of the same cube formed of asupport material formulation in which a mixture of 5% of an exemplarysecond curable material (HAA) and 5% of another exemplary second curablematerial was added to the first curable material (blank bar); and

FIG. 6 presents comparative plots showing the mechanical strength (N) asa function of deflection (M″M) measured for 30 grams of the F4formulation as described herein and 30 grams of a similar formulation inwhich the acrylamide monomer was replaced by an equivalent amount of IBOA, which were put in mold and cured in a UV oven for 5 hours.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

The present invention, in some embodiments thereof, relates to additivemanufacturing (AM), and more particularly, but not exclusively, toformulations useful for forming a support material in additivemanufacturing such as three-dimensional inkjet printing, and to methodsof additive manufacturing utilizing same.

Before explaining at least one embodiment of the invention in detail, itis to be understood that the invention is not necessarily limited in itsapplication to the details of construction and the arrangement of thecomponents and/or methods set forth in the following description and/orillustrated in the drawings and/or the Examples. The invention iscapable of other embodiments or of being practiced or carried out invarious ways.

The present inventors have searched for a support material formulationsuitable for use in additive manufacturing, as described herein, thatcan be removed from a printed object made upon dispensing theformulation, typically along with dispensing a modeling materialformulation, in low dissolution times and high dissolution rates,without compromising the mechanical properties of the cured supportmaterial.

Support material formulations typically comprise a water-misciblenon-curable polymer and a curable material. The curable material cancomprise a mono-functional curable material, and/or a multi-functionalcurable material and/or a cross-linking agent.

Cured support materials that are characterized by a mechanical strengththat is suitable for, for example, 3D inkjet printing, often comprise acurable material that upon curing, exhibits intermolecular interactionsbetween the polymeric chains formed upon exposing the support materialformulation to curing energy, that attribute to the mechanical strength.

Such intermolecular interactions include, for example, hydrogen bonds,electrostatic interactions, aromatic interactions, and chemicalcross-linking.

For example, cured support materials that are characterized by amechanical strength that is suitable for, for example, 3D inkjetprinting, may exhibit at least some degree of cross-linking, that is, atleast some of the polymeric chains formed upon exposing the supportmaterial formulation to curing energy, are chemically cross-linkedtherebetween.

Such a cross-linking can be obtained, for example, when the curablematerial comprises a multi-functional curable material and/or anothercross-linking agent.

By “chemical cross-linking” or “chemically cross-linked” it is meantthat the polymeric chains are linked to one another via covalent bonds,for example, two or more polymeric chains are each covalently bound tothe cross-linking compound (e.g., to a polymer formed frommulti-functional curable material).

The presence of chemically cross-linked polymeric chains in a curedsupport material is assumed to provide the cured support material withthe desired mechanical strength, yet, it also adversely affects thedissolution of the cured support material in an aqueous solution.

Cured support materials that exhibit some degree of cross-linking, orotherwise exhibit high mechanical strength as a result of intermolecularinteractions as described herein, are often not water-soluble, andrequire harsh conditions, for example, concentrated alkaline solutions,for effecting chemical dissolution thereof.

The present inventors have studied the effect of reducing aconcentration of a multi-functional curable material on the dissolutionrate and time of a cured support material, and have uncovered that whilethe dissolution rate indeed increases, the mechanical strength of thecured support material is adversely decreased.

While searching for a solution to this problem, the present inventorshave uncovered that introducing to a support material formulation acurable material, which is capable of interfering with theintermolecular interactions described herein, while reducing theconcentration of multi-functional curable material in the formulation,results in support material formulations that upon exposure to curingenergy provide a cured support material that is characterized by thedesired reduced dissolution time and increased dissolution rate, whilemaintaining a desirable mechanical strength.

The present inventors have designed and successfully prepared andpracticed novel support material formulations, which can easily andefficiently be removed by dissolution in an alkaline solution, withoutcompromising the mechanical strength of the cured support materialformed upon exposing the formulation to a suitable curing energy, asdescribed herein. The present inventors have shown that these novelformulations are usable for forming a soluble hardened support materialin 3D inkjet printing methods, and exhibit improved performance comparedto currently known and/or available formulations for forming solublehardened support materials.

Herein throughout, the term “object” or “printed object” describes aproduct of the manufacturing process. This term refers to the productobtained by a method as described herein, before removal of the supportmaterial. A printed object is therefore made of hardened (e.g., cured)modeling material and hardened (e.g., cured) support material.

The term “printed object” as used herein throughout refers to a wholeprinted object or a part thereof.

The term “model”, as used herein, describes a final product of themanufacturing process. This term refers to the product obtained by amethod as described herein, after removal of the support material. Themodel therefore essentially consists of a cured modeling material,unless otherwise indicated. This term is also referred to herein as“model object”, “final object” or simply as “object”.

The terms “model”, “model object”, “final object” and “object”, as usedherein throughout, refer to a whole object or a part thereof.

Herein throughout, the phrase “uncured building material” collectivelydescribes the materials that are dispensed during the fabricationprocess so as to sequentially form the layers, as described herein. Thisphrase encompasses uncured materials dispensed so as to form the printedobject, namely, one or more uncured modeling material formulation(s),and uncured materials dispensed so as to form the support, namelyuncured support material formulations.

Herein throughout, the phrases “cured modeling material” and “hardenedmodeling material”, which are used interchangeably, describe the part ofthe building material that forms a model object, as defined herein, uponexposing the dispensed building material to curing, and followingremoval of the cured support material. The cured modeling material canbe a single cured material or a mixture of two or more cured materials,depending on the modeling material formulations used in the method, asdescribed herein.

Herein throughout, the phrase “modeling material formulation”, which isalso referred to herein interchangeably as “modeling formulation” orsimply as “formulation”, describes a part of the uncured buildingmaterial which is dispensed so as to form the model object, as describedherein. The modeling formulation is an uncured modeling formulation,which, upon exposure to curing energy, forms the final object or a partthereof.

An uncured building material can comprise one or more modelingformulations, and can be dispensed such that different parts of themodel object are made upon curing different modeling formulations, andhence are made of different cured modeling materials or differentmixtures of cured modeling materials.

Herein throughout, the phrase “hardened support material” is alsoreferred to herein interchangeably as “cured support material” or simplyas “support material” and describes the part of the building materialthat is intended to support the fabricated final object during thefabrication process, and which is removed once the process is completedand a hardened modeling material is obtained.

Herein throughout, the phrase “support material formulation”, which isalso referred to herein interchangeably as “support formulation” orsimply as “formulation”, describes a part of the uncured buildingmaterial which is dispensed so as to form the support material, asdescribed herein. The support material formulation is an uncuredformulation, which, upon exposure to curing energy, forms the hardenedsupport material.

Herein throughout, the term “water-miscible” describes a material whichis at least partially dissolvable or dispersible in water, that is, atleast 50% of the molecules move into the water upon mixture. This termencompasses the terms “water-soluble” and “water dispersible”.

Herein throughout, the term “water-soluble” describes a material thatwhen mixed with water in equal volumes or weights, a homogeneoussolution is formed.

Herein throughout, the term “water-dispersible” describes a materialthat forms a homogeneous dispersion when mixed with water in equalvolumes or weights.

Herein throughout, the phrase “dissolution rate” describes a rate atwhich a substance is dissolved in a liquid medium. Dissolution rate canbe determined, in the context of the present embodiments, by the timeneeded to dissolve a certain amount of support material. The measuredtime is referred to herein as “dissolution time”.

Herein throughout, whenever the phrase “weight percents” is indicated inthe context of embodiments of a support material formulation, it ismeant weight percents of the total weight of the uncured supportmaterial formulation as described herein.

The phrase “weight percents” is also referred to herein as “% by weight”or “% wt.”.

Herein throughout, some embodiments of the present invention aredescribed in the context of the additive manufacturing being a 3D inkjetprinting. However, other additive manufacturing processes, such as, butnot limited to, SLA and DLP, are contemplated.

The Support Material Formulations:

The present inventors have designed and successfully prepared andpracticed a support material formulation which provides a cured supportmaterial that is characterized, for example, as follows:

by a dissolution time of a 20×20×20 mm cube made of the cured supportmaterial and immersed in 800 mL of the alkaline solution which is lessthan 10 hours, or less than 5 hours, or less than 2 hours, wherein thealkaline solution comprises 2% wt. NaOH and 1% wt. sodium metasilicate;and

by a mechanical strength of a 20 mm×20 mm×20 mm cube made of the supportmaterial formulation of at least 100 N, as determined by a compressiontest as described in the Examples section that follows.

According to an aspect of some embodiments of the present invention,there is provided a support material formulation which comprises:

a non-curable water-miscible polymer;

a first water-miscible, curable material; and

at least one second water-miscible curable material.

Herein throughout, a “curable material” is a compound or a mixture ofcompounds (monomeric and/or oligomeric and/or polymeric compounds)which, when exposed to curing energy, as described herein, solidify orharden to form a cured support material as defined herein. Curablematerials are typically polymerizable materials, which undergopolymerization and/or cross-linking when exposed to suitable energysource.

A “curable material” is also referred to herein and in the art as“reactive” material.

In some of any of the embodiments described herein, a curable materialis a photopolymerizable material, which polymerizes or undergoescross-linking upon exposure to radiation, as described herein, and insome embodiments the curable material is a UV-curable material, whichpolymerizes or undergoes cross-linking upon exposure to UV-visradiation, as described herein.

In some embodiments, a curable material as described herein is apolymerizable material that polymerizes via photo-induced radicalpolymerization.

In some of any of the embodiments described herein, a curable materialcan comprise a monomer, and/or an oligomer and/or a short-chain polymer,each being polymerizable as described herein.

In some of any of the embodiments described herein, when a curablematerial is exposed to curing energy (e.g., radiation), it polymerizesby any one, or combination, of chain elongation and cross-linking.

In some of any of the embodiments described herein, a curable materialis a monomer or a mixture of monomers which can form a polymeric supportmaterial upon a polymerization reaction, when exposed to curing energyat which the polymerization reaction occurs. Such curable materials arealso referred to herein as “monomeric curable materials”, or as “curablemonomers”.

In some of any of the embodiments described herein, a curable materialis a polymer or an oligomer or a mixture of polymers and/or oligomerswhich can form a polymeric support material upon a polymerizationreaction, when exposed to curing energy at which the polymerizationreaction occurs.

A curable material can comprise a mono-functional curable materialand/or a multi-functional curable material.

Herein, a mono-functional curable material comprises one functionalgroup that can undergo polymerization when exposed to curing energy(e.g., radiation). A multi-functional curable material comprises two ormore groups that can undergo polymerization when exposed to curingenergy (e.g., radiation), and which in addition can participate inchemical cross-linking of polymeric chains formed upon exposure tocuring energy.

In some of any of the embodiments described herein, the curablematerials described herein are water-soluble or at least water-miscible,e.g., water-dispersible, as defined herein.

The Second Curable Material:

According to some embodiments of the present invention, the secondcurable material is selected capable of interfering with intermolecularinteractions, as described herein, between polymeric chains formed uponexposing the first water-miscible material to curing energy.

According to some embodiments of the present invention, the secondcurable material is selected capable of forming hydrogen bonds with thepolymeric chains formed upon exposing the first water-soluble materialto curing energy.

According to some embodiments of the present invention, the secondcurable material is selected capable of interfering with a chemicalcross-linking, as defined herein, between the polymeric chains formedupon exposing the first water-soluble material to curing energy.

According to some embodiments of the present invention, the secondcurable material is selected capable of reducing a degree of a chemicalcross-linking between the polymeric chains.

As discussed above, chemical cross-linking in a cured support materialcan be formed when a multi-functional curable material is present in thesupport material formulation.

In some embodiments, the second curable material is capable ofinterfering in, or reducing the degree of, chemical cross-linking thatis imparted by a multi-functional curable material that is present inthe support material formulation.

In some embodiments, the second curable material is capable of forminghydrogen bonds with the polymeric chains formed upon curing the firstcurable material, and thereby reduces the intermolecular interactionsbetween these polymeric chains and/or reduces the degree of chemicalcross-linking between the polymeric chains.

According to some of any of the embodiments described herein, the firstcurable material comprises a mixture of a mono-functional curablematerial, as described herein, and a multi-functional (e.g.,di-functional) curable material, as described herein.

According to some of any of the embodiments described herein, the secondcurable material features at least two hydrogen bond-forming chemicalmoieties.

The phrase “hydrogen bond-forming chemical moiety” or “hydrogenbond-forming moiety”, as used herein, describes a moiety, or group, oratom, that is capable of forming hydrogen bonds by being a hydrogen bonddonor or a hydrogen bond acceptor. Certain chemical moieties or groupscan include both a hydrogen bond donor and a hydrogen bond acceptor.

As used herein and known in the art, a “hydrogen bond” is a relativelyweak bond that forms a type of dipole-dipole attraction which occurswhen a hydrogen atom bonded to a strongly electronegative atom exists inthe vicinity of another electronegative atom with a lone pair ofelectrons.

The hydrogen atom in a hydrogen bond is partly shared between tworelatively electronegative atoms.

Hydrogen bonds typically have energies of 1-3 kcal mol⁻¹ (4-13 kJmol⁻¹), and their bond distances (measured from the hydrogen atom)typically range from 1.5 to 2.6 Å.

A hydrogen-bond donor is the group that includes both the atom to whichthe hydrogen is more tightly linked and the hydrogen atom itself,whereas a hydrogen-bond acceptor is the atom less tightly linked to thehydrogen atom. The relatively electronegative atom to which the hydrogenatom is covalently bonded pulls electron density away from the hydrogenatom so that it develops a partial positive charge (δ⁺). Thus, it caninteract with an atom having a partial negative charge (δ⁻) through anelectrostatic interaction.

Atoms that typically participate in hydrogen bond interactions, both asdonors and acceptors, include oxygen, nitrogen and fluorine. These atomstypically form a part of chemical group or moiety such as, for example,carbonyl, carboxylate, amide, hydroxyl, amine, imine, alkylfluoride, F₂,and more. However, other electronegative atoms and chemical groups ormoieties containing same may participate in hydrogen bonding.

According to some of any of the embodiments described herein, each ofthe two or more hydrogen bond-forming chemical moieties in the secondcurable material independently comprises one or more oxygen atoms and/ornitrogen atoms, which participate in hydrogen bond formation, asdescribed herein.

Exemplary hydrogen bond-forming chemical moieties include, but are notlimited to, amide, carboxylate, hydroxy, alkoxy, aryloxy, ether, amine,carbamate, hydrazine, a nitrogen-containing heteralicyclic (e.g.,piperidine, oxalidine), and an oxygen-containing heteralicyclic (e.g.,tetrahydrofuran, morpholine), and any other chemical moiety thatcomprises one or more nitrogen and/or oxygen atoms.

The hydrogen bond-forming moieties in the second curable monomer can beseparated from one another by, for example, 2-20, or 2-10, or 2-8, or2-6 or 2-4 atoms, including any subranges and intermediate valuestherebetween, which can be regarded as a linking moiety linking betweenthe hydrogen bind-forming moieties.

Thus, in some embodiments, the distance between at least two of thehydrogen bond-forming chemical moieties is of, for example, 2-10, or2-8, or 2-6 or 2-4 atoms.

In some embodiments, the two or more hydrogen bond-forming chemicalmoieties are separated from one another by an alkylene chain, and hencethe above-described atoms are carbon atoms.

According to some of any of the embodiments described herein, the secondcurable material is a UV-curable material, as described herein.

According to some of any of the embodiments described herein, the secondcurable material is an acrylate. The carboxylate in the acrylate is ahydrogen bond-forming moiety as described herein.

According to some of any of the embodiments described herein, the secondcurable material is an acrylamide. The amide in the acrylamide is ahydrogen bond-forming moiety as described herein.

According to some of any of the embodiments described herein, the secondcurable material is an acrylamide substituted by one or hydrogenbond-forming chemical moiety or moieties, as described herein. In someembodiments, a hydrogen bond-forming moiety and the amide (which isanother hydrogen bond-forming moiety) are linked to one another, orseparated, by an alkyl.

In some embodiments, the second curable material is an acrylamidesubstituted by a chemical moiety such as, but not limited tohydroxyalkyl, alkoxyalkyl, aminoalkyl, alkylaminoalkyl,dialkylaminoalkyl, carboxyalkyl, hidrazinoalkyl, carbamoylalkyl, and analkyl substituted by any other hydrogen bond-forming chemical moiety asdescribed herein.

In some embodiments, the alkyl is a C(1-10) alkyl, or a C(2-10) alkyl,or a C(2-8) alkyl, or a C(2-6) alkyl, or a C(2-4) alkyl, or is ethyl.

According to some of any of the embodiments described herein, the secondcurable material is represented by Formula I:

wherein:

Ra is selected from H, C(1-4) alkyl (e.g., methyl) or, optionally, canbe a hydrophilic group, as described herein;

k is an integer ranging from 1 to 10, or from 2-10, or from 2 to 8, orfrom 2 to 6, or from 2 to 4, or is 2 or 3; and

X and Y are each independently a hydrogen bond-forming moiety thatcomprises at least one nitrogen and/or oxygen atom, as described herein.

In some embodiments, Y can be hydroxyl, alkoxy, aryloxy, amine,alkylamine, dialkylamine, carboxylate, hydrazine, carbamate, hydrazine,a nitrogen-containing heteralicyclic, and an oxygen-containingheteralicyclic, as defined herein.

In some embodiments, X is —O—, and in some of these embodiments, Ra isH, such that the second curable material is an acrylate. When Ra ismethyl, the second curable material is a methacrylate.

In some embodiments, X is —NRc-, wherein Rc can be, for example,hydrogen, alkyl, cycloalkyl or aryl, wherein the alkyl, cycloalkyl andaryl can be substituted or unsubstituted, as described herein. In theseembodiments, when Ra is H, the second curable material is an acrylamide.When Ra is methyl, the second curable material is methacrylamide.

In some of any of the embodiments described herein, the second curablematerial is represented by Formula I, wherein:

X is NH; k is 2 or 3, and Y is hydroxyl.

In some of any of the embodiments described herein, the second curablematerial is represented by Formula I, wherein:

X is NH; k is 2 or 3, and Y is amine, alkylamine or dialkylamine, forexample, dimethylamine.

In some of any of the embodiments described herein, the second curablematerial is represented by Formula I, wherein:

Ra is H; X is NH; k is 2 or 3, and Y is hydroxyl.

In some of any of the embodiments described herein, the second curablematerial is represented by Formula I, wherein:

Ra is methyl; X is NH; k is 2 or 3, and Y is hydroxyl.

In some of any of the embodiments described herein, the second curablematerial is represented by Formula I, wherein:

Ra is H, X is NH; k is 2 or 3, and Y is dimethylamine.

In some of any of the embodiments described herein, the second curablematerial is represented by Formula I, wherein:

Ra is methyl, X is NH; k is 2 or 3, and Y is dimethylamine.

In some of any of the embodiments described herein, the second curablematerial comprises one or more curable materials or one or more of anyof the compounds described in any of the respective embodiments herein.

In some of any of the embodiments described herein, the second curablematerial comprises a mixture of two or more curable materialsrepresented by Formula I herein, and is some embodiments it comprisestwo or more substituted acryl amides as described herein.

In some of any of the embodiments described herein, one or more ofcurable materials in the second curable material is characterized by aTg of a polymer formed therefrom which is higher than 100° C., or higherthan 110° C., or higher than 120° C., or higher than 130° C.

The First Curable Material:

In some of any of the embodiments described herein, the first curablematerial is a UV-curable material.

In some of any of the embodiments described herein, each of the firstand second mono-functional materials is a UV-curable material.

In some of any of the embodiments described herein, each of the firstand second mono-functional materials independently comprises anacrylate, a methacrylate, an acrylamide or a methacrylamide curablemoiety (or moieties).

In some of any of the embodiments described herein, the first curablematerial comprises a mono-functional curable material.

In some of any of the embodiments described herein, the first curablematerial comprises a multi-functional, e.g., di-functional curablematerial.

In some of any of the embodiments described herein, the first curablematerial comprises a mixture of a multi-functional, e.g., di-functionalcurable material and a mono-functional curable material.

A curable mono-functional material forming the first curable materialaccording to some embodiments of the present invention can comprise oneor more of a vinyl-containing compound represented by Formula II:

The (═CH₂) group in Formula I represents a polymerizable group, and istypically a UV-curable group, such that the material is a UV-curablematerial.

In some embodiments, R₁ is a carboxylate, and the compound is amono-functional acrylate. In some of these embodiments, R₂ is methyl,and the compound is mono-functional methacrylate. In other embodiments,R₂ is hydrogen, and the compound is a mono-functional acrylate. R₂ canbe hydrogen, a C(1-4) alkyl, or can be a hydrophilic group.

In some of any of these embodiments, the carboxylate group is—C(═O)—OR′, with R′ being selected from, for example, alkyl, cycloalkyl,heteroalicyclic groups containing nitrogen and/or oxygen atoms such asmorpholine, tetrahydrofuran, oxalidine, and the likes, C(1-4)alkyloptionally substituted or interrupted by one or more of e.g., hydroxy,—O—, amine or —NH—), hydroxy, thiol, an alkylene glycol, a poly(alkyleneglycol) or an oligo(alkylene glycol).

An exemplary mono-functional curable material forming the first curablematerial is a poly(alkylene glycol) acrylate such as poly(ethyleneglycol) acrylate. Other water soluble acrylate or methacrylatemono-functional monomers are contemplated.

An exemplary mono-functional curable material forming the first curablematerial is represented by Formula IV:

wherein:

n is an integer ranging from 2 to 10, or from 2 to 8;

m is an integer ranging from 2 to 6, preferably from 2 to 4, or is 2 or3;

R′ can be hydrogen, alkyl, cycloalkyl, or aryl; and

Ra is H or C(1-4) alkyl.

In some of any of the embodiments of Formula IV, R′ is hydrogen.

In some of any of the embodiments of Formula IV, m is 2, and Ra is H,such that the compound is a poly(ethylene glycol) acrylate.

In some of any of the embodiments of Formula IV, m is 2, and Ra ismethyl, such that the compound is a poly(ethylene glycol) methacrylate.In some of any of the embodiments of Formula IV, R′ is H, and is some ofany of the embodiments of Formula IV, n is 4, 5, 6, 7 or 8, for example,6.

In some embodiments, R₁ in Formula II is amide, and the compound is amono-functional acrylamide. In some of these embodiments, R₂ is methyl,and the compound is mono-functional methacrylamide. In some of theseembodiments, the amide is substituted. For example, the amide group is—C(═O)—NR′R″ wherein R′ and R″ are as described herein. An exemplarysuch monomer includes acryloyl morpholine (ACMO). Other water solubleacrylamide or methacrylamide mono-functional monomers are contemplated.

In some embodiments, one or both of R₁ and R₂ is a group other thancarboxylate or amide, for example, is a cyclic amide (lactam), a cyclicester (lactone), a phosphate, phosphonate, sulfate, sulfonate, alkoxy,substituted alkoxy, or else. In such embodiments, the curable materialis a substituted vinyl monomer. Exemplary such vinyl monomers are vinylphosphonic acid and hydroxybutyl vinyl ether. Other water solublemono-functional vinyl ethers or otherwise substituted vinyl monomers arecontemplated.

In some of any of the embodiments described herein, the first curablematerial comprises one or more of the mono-functional curable monomersas described herein.

In some of any of the embodiments described herein, a di-functionalcurable monomer that may form a part of the first curable material,optionally and preferably in addition to the mono-functional curablematerial described in the connect of the first curable material, isrepresented by the Formula III:

wherein:

each of R₃ and R₄ is independently hydrogen, C(1-4)alkyl, or ahydrophilic group;

L is a linking moiety; and

each of X₁ and X₂ is independently a carboxylate, an amide, or any othergroup as defined herein for R₁ in Formula II.

Di-functional curable monomers of Formula III in which one or both of X₁and X₂ is carboxylate, are di-functional acrylates. When one or more ofR₃ and R₄ is methyl, the curable monomer is a di-functionalmethacrylate.

In some embodiments, L is a polymeric or oligomeric moiety. In someembodiments, L is or comprises an alkylene glycol moiety, or apoly(alkylene glycol) moiety. In some embodiments, L is an alkylenemoiety, optionally interrupted by one or more heteroatoms such as O, Sor by NR′.

Exemplary di-functional curable monomers include polyethylene glycoldiacrylate, polyethylene glycol dimethacrylate, polyethyleneglycol-polyethylene glycol urethane diacrylate, and a partiallyacrylated polyol oligomer.

In some embodiments of Formula III, R₃ and R₄ are each hydrogen, and X₁and X₂ are each carboxylate, such that the di-functional curablematerial is a diacrylate.

In some of these embodiments, L is a poly(alkylene glycol).

In some of any of the embodiments described herein, a di-functionalcurable material forming a part of the first curable material is apoly(alkylene glycol) diacrylate represented by Formula V:

wherein:

n is an integer ranging from 2 to 40, or from 2 to 20, or from 2 to 10,or from 2 to 8;

m is an integer ranging from 2 to 6, preferably from 2 to 4, or is 2 or3; and

Ra and Rb are each independently H or C(1-4) alkyl.

In some of these embodiments, Ra and Rb are each H.

In some of these embodiments, m is 2.

In some of these embodiments, n is 4, 5, 6, 7 or 8, for example, 6.

In some embodiments of Formula III, one or both of X₁ and X₂ is —O—,such that at least one functional moiety in the di-functional curablematerial is vinyl ether.

Multi-functional curable materials contemplated in embodiments of thefirst curable material can be, for example, of Formula III, as describedherein, wherein the L linking moiety is substituted by one or moietiesthat independently comprise a —X₃—C(═O)—CR₅═CH₂, wherein X₃ is asdescribed herein for X₁ and X₂, and R₅ is as described herein for R₃ andR₄.

Other multi-functional curable materials and mono-functional curablematerials known in the art as usable in support material formulationsare also contemplated.

In some of any of the embodiments described herein, the support materialformulation comprises a mixture of a mono-functional curable materialand a multi-functional curable material, and in some of theseembodiments the multi-functional curable material is a di-functionalcurable material as described herein in any of the respectiveembodiments and any combination thereof.

Any other curable monomer that is usable for forming cured supportmaterials in AM processes is contemplated herein as included in asupport material formulation, in addition to, or instead of, the curablematerials described herein.

Exemplary other curable monomers include, without limitation,diacrylates such as polyurethane diacrylate oligomer and/or monomericdiacrylates, preferably short chain diacrylates such as, but not limitedto, isobornyl diacrylate.

In some of any of the embodiments described herein, the first curablematerial comprises a poly(alkylene glycol) acrylate, as describedherein.

In some of any of the embodiments described herein, the first curablematerial comprises a mono-functional poly(alkylene glycol) acrylate(e.g., Formula IV).

In some of any of the embodiments described herein, the first curablematerial comprises a mixture of a mono-functional poly(alkylene glycol)acrylate and a multi-functional, e.g., di-functional, poly(alkyleneglycol) acrylate.

In some of any of the embodiments described herein, the first curablematerial comprises a mixture of a poly(alkylene glycol) acrylate (e.g.,of Formula IV) and a poly(alkylene glycol) diacrylate (e.g., of FormulaV).

In some of any of these embodiments the poly(alkylene glycol) ispoly(ethylene glycol).

In some of these embodiments, a weight ratio between the mono-functionalpoly(alkylene glycol) acrylate and the di-functional poly(alkyleneglycol) acrylate (e.g., poly(alkylene glycol) diacrylate) in the firstcurable material ranges from 70:30 to 95:5, and can be, for example,70:30, 75:25, 80:20, 85:15, 90:10 or 95:5.

In some of any of the embodiments described herein, the first curablematerial comprises a mixture of a mono-functional curable material and amulti-functional curable material, and a weight ratio between thesematerials ranges from 50:50 to 95:5, and can be, for example, 50:50,60:40, 70:30, 75:25, 80:20, 85:15, 90:10 or 95:5.

The Water Miscible Non-Curable Polymer:

In some of any of the embodiments described herein, a support materialformulation comprises, in addition to the curable monomers, awater-miscible polymeric material, which can be any of thewater-miscible polymeric materials commonly used in support materialformulations.

In some of any of the embodiments described herein, the water-misciblepolymeric material is non-curable (also referred to herein as“non-reactive”). The term “non-curable” encompasses polymeric materialsthat are non-polymerizable under any conditions or polymeric materialsthat are non-curable under conditions at which the mono-functionalmonomer as described herein is curable, or under any condition used in afabrication of an object. Such polymeric materials are typically devoidof a polymerizable group or of a UV-photopolymerizable group. In someembodiments, the polymeric material is non-reactive towards the curablemonomer as described herein, that is, it does not react with the monomerand is incapable of interfering with the curing of the monomer, underthe fabrication conditions, including the curing conditions.

In some of any of the embodiments described herein the polymericmaterial is water soluble or water dispersible or water misciblepolymeric material, as defined herein.

In some embodiments, the polymeric material comprises a plurality ofhydrophilic groups as defined herein, either within the backbone chainof the polymer or as pendant groups. Exemplary such polymeric materialsare polyols. Some representative examples include, but are not limitedto, Polyol 3165, polypropylene glycol, polyethylene glycol, polyglycerol, ethoxylated forms of these polymers, paraffin oil and thelike, and any combination thereof.

In some of any of the embodiments described herein, the support materialformulation further comprises a water-miscible, non-curable,non-polymeric material, such as, for example, propane diol (e.g.,1,2-propandoil).

In some of any of the embodiments described herein, the support materialformulation comprises a water-miscible, non-curable material whichcomprises a mixture of two or more or more of the polymeric andnon-polymeric water-miscible, non-curable materials described herein. Anexemplary such a mixture may comprise two or more of a polyethyleneglycol, a propane diol and a polyol such as Polyol 3165.

Additional Agents:

A support material formulation as described herein in any of therespective embodiments can further comprise additional agents, forexample, initiators, inhibitors, stabilizers and the like.

In some of any of the embodiments described herein, and any combinationthereof, the support material formulation further comprises aninitiator, for inducing a polymerization of the curable materials uponexposure to curing energy or curing conditions.

In some of these embodiments, one or more or all of the curablematerials is a UV-curable material and the initiator is aphotoinitiator.

The photoinitiator can be a free radical photo-initiator, a cationicphoto-initiator, or any combination thereof.

A free radical photoinitiator may be any compound that produces a freeradical upon exposure to radiation such as ultraviolet or visibleradiation and thereby initiates a polymerization reaction. Non-limitingexamples of suitable photoinitiators include phenyl ketones, such asalkyl/cycloalkyl phenyl ketones, benzophenones (aromatic ketones) suchas benzophenone, methyl benzophenone, Michler's ketone and xanthones;acylphosphine oxide type photo-initiators such as2,4,6-trimethylbenzolydiphenyl phosphine oxide (TMPO),2,4,6-trimethylbenzoylethoxyphenyl phosphine oxide (TEPO), andbisacylphosphine oxides (BAPO's); benzoins and benzoin alkyl ethers suchas benzoin, benzoin methyl ether and benzoin isopropyl ether and thelike. Examples of photoinitiators are alpha-amino ketone, and1-hydroxycyclohexyl phenyl ketone (e.g., marketed as Igracure® 184).

A free-radical photo-initiator may be used alone or in combination witha co-initiator. Co-initiators are used with initiators that need asecond molecule to produce a radical that is active in the UV-systems.Benzophenone is an example of a photoinitiator that requires a secondmolecule, such as an amine, to produce a curable radical. Afterabsorbing radiation, benzophenone reacts with a ternary amine byhydrogen abstraction, to generate an alpha-amino radical which initiatespolymerization of acrylates. Non-limiting example of a class ofco-initiators are alkanolamines such as triethylamine,methyldiethanolamine and triethanolamine.

Suitable cationic photoinitiators include, for example, compounds whichform aprotic acids or Bronstead acids upon exposure to ultravioletand/or visible light sufficient to initiate polymerization. Thephotoinitiator used may be a single compound, a mixture of two or moreactive compounds, or a combination of two or more different compounds,i.e. co-initiators. Non-limiting examples of suitable cationicphotoinitiators include aryldiazonium salts, diaryliodonium salts,triarylsulphonium salts, triarylselenonium salts and the like. Anexemplary cationic photoinitiator is a mixture of triarylsolfoniumhexafluoroantimonate salts.

In some of any of the embodiments described herein, the uncured supportmaterial formulation may further comprise one or more additional agentsthat are beneficially used in the fabrication process. Such agentsinclude, for example, surface active agents, inhibitors and stabilizers.

In some embodiments, a support material formulation as described hereincomprises a surface active agent. A surface-active agent may be used toreduce the surface tension of the formulation to the value required forjetting or for other printing process, which is typically around 30dyne/cm. An exemplary such agent is a silicone surface additive such as,but not limited to, a surface agent marketed as BYK-345.

In some embodiments, a support material formulation as described hereinfurther comprises an inhibitor, which inhibits pre-polymerization of thecurable material during the fabrication process and before it issubjected to curing conditions. An exemplary stabilizer (inhibitor) isTris(N-nitroso-N-phenylhydroxylamine) Aluminum Salt (NPAL) (e.g., asmarketed under FirstCure®NPAL).

Suitable stabilizers include, for example, thermal stabilizers, whichstabilize the formulation at high temperatures.

In some of any of the embodiments described herein, the support materialformulation is devoid of a silicon polyether.

Exemplary Support Material Formulations:

According to some of any of the embodiments described herein, thesupport material formulation is such that a concentration of thenon-curable water-miscible polymer ranges from 30% to 80% by weight ofthe total weight of the formulation.

According to some of any of the embodiments described herein, thesupport material formulation is such that a concentration of the secondcurable material ranges from 5% to 40% by weight of the total weight ofthe formulation. In some embodiments, a concentration of the secondcurable material ranges from 5% to 30%, or from 5% to 20%, or from 5% to10%, of the total weight of the formulation.

According to some of any of the embodiments described herein, thesupport material formulation is such that a concentration of the secondcurable monomer ranges from 1 to 40, or from 1 to 30, or from 1 to 20,or from 5 to 20, or from 5 to 15, or from 5 to 10, weight percents ofthe total weight of the formulation.

The second curable material according to these embodiments can be amixture of two or more curable materials and the above concentrationsapply to a total concentration of these materials.

When a mixture of two curable materials forms the second curablematerial, the weight ratio of these materials can be from 50:50 to 95:5,and can be, for example, 50:50, or 60:40, or 70:30, or 80:20, or 90:10,or 10:90, or 80:20, or 70:30, or 40:60.

According to some of any of the embodiments described herein, thesupport material formulation is such that a concentration of the firstcurable material ranges from 5 to 40, or from 5 to 30, or from 5 to 25,or from 5 to 20, or from 10 to 20, or from 5 to 15, or from 10 to 15,weight percents of the total weight of the formulation.

According to some of any of the embodiments described herein, thesupport material formulation is such that a concentration of the firstcurable material is lower than 30%, or lower than 20%, or lower than 15%by weight of the total weight of the formulation.

According to some of any of the embodiments described herein, thesupport material formulation is such that a total concentration of thefirst and second curable materials ranges from 10 to 45 weight percents,or from 10 to 40 weight percents, or from 10 to 30 weight percents, orfrom 15 to 45 weight percents, or from 10 to 20 weight percents, of thetotal weight of the formulation. Any combination of concentrations ofthe first and second curable materials is contemplated.

According to some of any of the embodiments described herein, thesupport material formulation is such that the first curable materialcomprises a mixture of a mono-functional curable material and amulti-functional (e.g., di-functional) curable material, at a weightratio as described herein, and a concentration of the mono-functionalcurable material ranges from 5 to 35 or from 5 to 30 weight percents ofthe total weight of the formulation, and the concentration of themulti-functional (e.g., di-functional) curable material ranges from 0.5to 10, or from 0.5 to 8, or from 0.5 to 5, weight percents, of the totalweight of the formulation.

According to some of any of the embodiments described herein, thesupport material formulation is such that:

a concentration of the water-miscible non-curable polymer ranges from30% to 80% by weight of the total weight of the formulation;

the first curable material comprises a mixture of a mono-functionalcurable material and a multi-functional (e.g., di-functional) curablematerial, at a weight ratio of, for example, 90:10;

a concentration of the mono-functional curable material ranges from 5 to35 or from 5 to 30 weight percents of the total weight of theformulation;

the concentration of the multi-functional (e.g., di-functional) curablematerial ranges from 0.5 to 10, or from 0.5 to 8, or from 0.5 to 5,weight percents, of the total weight of the formulation; and

the second curable material comprises one or two curable materials at atotal concentration of from 5 to 40, or from 5 to 15 weight percents ofthe total weight of the composition.

According to some of any of the embodiments described herein, thesupport material formulation is such that:

a concentration of the water-miscible non-curable polymer ranges from30% to 80% or from 40 to 80%, by weight of the total weight of theformulation;

the first curable material comprises a mono-functional curable materialat a concentration that ranges from 5 to 35 or from 10 to 30 weightpercents of the total weight of the formulation; and

the second curable material comprises a curable material at aconcentration of from 5 to 40, or from 5 to 15 weight percents of thetotal weight of the composition.

According to some of any of these embodiments, the first curablematerial comprises a poly(alkylene glycol) acrylate (e.g., of FormulaIV), optionally in combination with a poly(alkylene glycol) diacrylate(e.g., of Formula V). In some of any of these embodiments thepoly(alkylene glycol) is poly(ethylene glycol).

According to some of any of the embodiments described herein, theformulation is devoid of a multi-functional curable material, and issome embodiments, it is devoid of a poly(alkylene glycol) diacrylate(e.g., of Formula V).

According to some of any of the above embodiments, the second curablemonomer comprises a compound represented by Formula I, wherein:

Ra is H; X is NH; k is 2 or 3, and Y is hydroxyl.

In some of any of the above embodiments, the second curable materialcomprises a represented by Formula I, wherein:

Ra is methyl; X is NH; k is 2 or 3, and Y is hydroxyl.

In some of any of the above embodiments, the second curable materialcomprises a represented by Formula I, wherein:

Ra is H, X is NH; k is 2 or 3, and Y is dimethylamine.

In some of any of the above embodiments, the second curable materialcomprises a represented by Formula I, wherein:

Ra is methyl, X is NH; k is 2 or 3, and Y is dimethylamine.

According to some of these embodiments, the support material formulationfurther comprises an initiator (e.g., a photoinitiator) at aconcentration of from 0.1-2 weight percents of the total weight of thecomposition; and

a surfactant, at a concentration of 0 to 2 weight percents of the totalweight of the composition.

In some of any of the embodiments described herein, each of the curablematerials included in the support material formulation is a UV-curablematerial, as defined herein, for example, an acrylate or a methacrylateor an acrylamide or a methacrylamide (mono-functional ormulti-functional, monomeric or oligomeric).

Properties:

According to some of any of the embodiments described herein, thesupport material formulation exhibits a viscosity that is suitable for3D inkjet printing.

In exemplary embodiments, the viscosity of the modeling formulation islower than 30 cps, or lower than 25 cps, or lower than 20 cps, at theworking temperature. In some embodiments, the viscosity of theformulation is higher at room temperature and can be, for example, above50 cps, or above 80 cps, at room temperature.

In some of any of the embodiments described herein, the support materialformulation is such that exhibit a viscosity of from 10 to 20 cps atroom temperature. In some embodiments, the first and second curablematerials, and the polymeric material, and the concentration of each,are selected or manipulated such that the formulation exhibits a desiredviscosity as described herein (before curing).

According to some of any of the embodiments described herein, a curedsupport material formed upon exposing the formulation to a curing energyis dissolvable in an alkaline solution.

According to some of any of the embodiments described herein, adissolution time of the cured support material when immersed in thealkaline solution is at least 2-folds, or at least 4-folds, shorter thana dissolution time of a cured support material made of a comparablesupport material formulation that is absent the second curable material.

By “comparable support material formulation” it is meant a supportmaterial formulation that comprises a water-miscible non-curablepolymeric material as described herein and identical to a water-misciblepolymeric material of the support formulation, and a first curablematerial as described herein, wherein a concentration of the firstcurable material in the comparable formulation is substantially the sameas a total concentration of the first and second curable materials inthe support material formulation.

According to some of any of the embodiments described herein, adissolution time of a 16-grams cube (e.g., a 20 mm×20 mm×20 mm cube)made of the cured support material and immersed in 800 mL of thealkaline solution is less than 10 hours, or less than 5 hours, or lessthan 2 hours, preferably less than 2 hours

According to some embodiments, the alkaline solution comprises an alkalimetal hydroxide.

According to some embodiments, the alkaline solution further comprisesan alkali metal silicate.

According to some embodiments, the support material formulation is suchthat a cured support material made therefrom is dissolvable in analkaline solution that comprises a mixture of an alkali metal hydroxideand an alkali metal silicate, and the above dissolution times are withrespect to such an alkaline solution.

In some embodiments, the alkaline solution comprises an alkali metalsilicate at a concentration that ranges from 1 to 3 weight percent ofthe total weight of the solution, and an alkali metal hydroxide at aconcentration that ranges from 1 to 3 weight percents of the totalweight of the solution.

In some embodiments of the alkaline solution, a concentration of thealkali metal hydroxide is 2 weight percents of the total weight of thesolution.

In some embodiments of the alkaline solution, a concentration of thealkali metal silicate is 1 weight percent of the total weight of thesolution.

In some embodiments of the alkaline solution, the alkaline solutioncomprises sodium hydroxide at a concentration that ranges from 1-3weight percents, or at a concentration of 2 weight percents; and sodiummetasilicate at a concentration of 1-3 weight percents, or at aconcentration of 1 weight percent.

According to some of any of the embodiments described herein, a 20 mm×20mm×20 mm object made of the support material formulation and formed uponexposing the formulation to a curing energy is characterized by amechanical strength of at least 100 N.

In some embodiments of the alkaline solution, a cured support materialformed upon exposing the formulation to a curing energy is characterizedby a mechanical strength that is lower from a mechanical strength of acured support material made of a comparable support material formulationthat is absent the second curable material, as defined herein, whichcomprises substantially the same total concentration of curablematerials as the formulation, by no more than 50% or by no more than40%, or by no more than 30%.

Model Fabrication:

According to an aspect of some embodiments of the present inventionthere is provided a method of fabricating a three-dimensional modelobject, which utilizes a support material formulation as describedherein. The method is also referred to herein as a fabrication processor as a model fabrication process. In some embodiments, the methodcomprises dispensing an uncured building material so as to sequentiallyform a plurality of layers in a configured pattern corresponding to theshape of the object. In some embodiments, the (uncured) buildingmaterial comprises a modeling material formulation and a supportmaterial formulation as described herein in any of the respectiveembodiments.

The modeling material formulation can be any modeling materialformulation used in additive manufacturing such as 3D inkjet printing,and is preferably curable under the same conditions at which the supportmaterial formulation is curable. The support material formulation is asdescribed herein in any of the respective embodiments and anycombination thereof.

According to some embodiments of the present invention, the fabricationmethod is additive manufacturing of a three-dimensional model object.

According to some embodiments of this aspect, formation of each layer iseffected by dispensing at least one uncured building material, andexposing the dispensed building material to curing energy or curingconditions, to thereby form a cured building material, which iscomprised of a cured modeling material and a cured support material.

According to some of any of the embodiments described herein, theadditive manufacturing is preferably by three-dimensional inkjetprinting.

The method of the present embodiments manufactures three-dimensionalobjects in a layerwise manner by forming a plurality of layers in aconfigured pattern corresponding to the shape of the objects.

Each layer is formed by an additive manufacturing apparatus which scansa two-dimensional surface and patterns it. While scanning, the apparatusvisits a plurality of target locations on the two-dimensional layer orsurface, and decides, for each target location or a group of targetlocations, whether or not the target location or group of targetlocations is to be occupied by building material, and which type ofbuilding material (e.g., a modeling material formulation or a supportmaterial formulation) is to be delivered thereto. The decision is madeaccording to a computer image of the surface.

When the AM is by three-dimensional printing, an uncured buildingmaterial, as defined herein, is dispensed from a dispensing head havinga set of nozzles to deposit building material in layers on a supportingstructure. The AM apparatus thus dispenses building material in targetlocations which are to be occupied and leaves other target locationsvoid. The apparatus typically includes a plurality of dispensing heads,each of which can be configured to dispense a different buildingmaterial. Thus, different target locations can be occupied by differentbuilding materials (e.g., a modeling formulation and/or a supportformulation, as defined herein).

In some of any of the embodiments of this aspect of the presentinvention, the method begins by receiving 3D printing data correspondingto the shape of the object. The data can be received, for example, froma host computer which transmits digital data pertaining to fabricationinstructions based on computer object data, e.g., in a form of aStandard Tessellation Language (STL) or a StereoLithography Contour(SLC) format, Virtual Reality Modeling Language (VRML), AdditiveManufacturing File (AMF) format, Drawing Exchange Format (DXF), PolygonFile Format (PLY) or any other format suitable for Computer-Aided Design(CAD).

Next, droplets of the uncured building material as described herein aredispensed in layers, on a receiving medium, using at least two differentmulti-nozzle inkjet printing heads, according to the printing data. Thereceiving medium can be a tray of a three-dimensional inkjet system or apreviously deposited layer. The uncured building material comprises asupport material formulation as described herein for any of therespective embodiments and any combination thereof.

In some embodiments of the present invention, the dispensing is effectedunder ambient environment.

Optionally, before being dispensed, the uncured building material, or apart thereof (e.g., one or more formulations of the building material),is heated, prior to being dispensed. These embodiments are particularlyuseful for uncured building material formulations having relatively highviscosity at the operation temperature of the working chamber of a 3Dinkjet printing system. The heating of the formulation(s) is preferablyto a temperature that allows jetting the respective formulation througha nozzle of a printing head of a 3D inkjet printing system. In someembodiments of the present invention, the heating is to a temperature atwhich the respective formulation exhibits a viscosity of no more than Xcentipoises, where X is about 30 centipoises, preferably about 25centipoises and more preferably about 20 centipoises, or 18 centipoises,or 16 centipoises, or 14 centipoises, or 12 centipoises, or 10centipoises.

The heating can be executed before loading the respective formulationinto the printing head of the 3D printing system, or while theformulation is in the printing head or while the composition passesthrough the nozzle of the printing head.

In some embodiments, the heating is executed before loading of therespective composition into the printing head, so as to avoid cloggingof the printing head by the composition in case its viscosity is toohigh.

In some embodiments, the heating is executed by heating the printingheads, at least while passing the first and/or second compositionthrough the nozzle of the printing head.

Once the uncured building material is dispensed on the receiving mediumaccording to the 3D printing data, the method optionally and preferablycontinues by exposing the dispensed building material to conditions theeffect curing. In some embodiments, the dispensed building material isexposed to curing energy by applying curing energy to the depositedlayers. Preferably, the curing is applied to each individual layerfollowing the deposition of the layer and prior to the deposition of theprevious layer.

The curing energy or condition can be, for example, a radiation, such asan ultraviolet or visible irradiation, or other electromagneticradiation, or electron beam radiation, depending on the buildingmaterial used. The curing energy or condition applied to the dispensedlayers serves for curing or solidifying or hardening the modelingmaterial formulation and the support material formulation. Preferably,the same curing energy or condition is applied to effect curing of boththe modeling materials and the support material. Alternatively,different curing energies or conditions are applied to the dispensedbuilding material, simultaneously or sequentially, to effect curing ofthe modeling material formulation and the support material formulation.

According to some of any of the embodiments of this aspect of thepresent invention, once the building material is dispensed to form anobject and curing energy or condition is applied, the cured supportmaterial is removed, to thereby obtain the final three-dimensionalobject.

According to some of any of the embodiments described herein, thesupport material is removed by contacting the cured support materialwith a cleaning composition for example, an alkaline solution asdescribed in any of the respective embodiments described herein, and anycombination thereof.

Contacting may be effected by means known in the art, for example, byimmersing the printed object is an aqueous solution, e.g., an alkalinesolution, and/or by jetting the alkaline solution onto the object. Thecontacting can be effected manually or in an automated manner. Anysystem or apparatus usable for removing a cured support material iscontemplated.

In some of any of the embodiments described herein, the contacting iseffected for a time period that is in correlation with the amount of thecured support material in the printed object, and the geometry thereof.For example, for a 16-grams, 20×20×20 mm cube made solely of anexemplary support material formulation as described herein thecontacting is effected for a time period of no more than 120 minutes.

In some embodiments, the contacting is effected during a time periodthat is shorter by at least 20%, at least 30%, at least 40%, at least50%, and even by 60%, 100%, 200%, 300%, 400 $ or shorter, compared to atime period required to remove a cured support material made of acomparable support material formulation as defined herein.

In some embodiments, the contacting is effected without replacing thecleaning composition (e.g., without introducing a fresh batch of acleaning composition to the apparatus or system where removal of thecured support material is performed).

In some of any of the embodiments described herein, removal of thesupport material is effected by mechanical removal of the cured supportmaterial, either alone or in combination with dissolution in an alkalinesolution as described herein. Any means known in the art formechanically removing a support material are contemplated.

Any system suitable for AM of an object (e.g., a model object) is usablefor executing the method as described herein.

A representative and non-limiting example of a system suitable for AM ofan object according to some embodiments of the present inventioncomprises an additive manufacturing apparatus having a dispensing unitwhich comprises a plurality of dispensing heads. Each head preferablycomprises an array of one or more nozzles, through which a liquid(uncured) building material is dispensed.

Preferably, but not obligatorily, the AM apparatus is athree-dimensional inkjet printing apparatus, in which case thedispensing heads are inkjet printing heads, and the building material isdispensed via inkjet technology. This need not necessarily be the case,since, for some applications, it may not be necessary for the additivemanufacturing apparatus to employ three-dimensional printing techniques.Representative examples of additive manufacturing apparatus contemplatedaccording to various exemplary embodiments of the present inventioninclude, without limitation, binder jet powder based apparatus, fuseddeposition modeling apparatus and fused material deposition apparatus.

Each dispensing head is optionally and preferably fed via one or morebuilding material reservoir(s) which may optionally include atemperature control unit (e.g., a temperature sensor and/or a heatingdevice), and a material level sensor. To dispense the building material,a voltage signal is applied to the dispensing heads to selectivelydeposit droplets of material via the dispensing head nozzles, forexample, as in piezoelectric inkjet printing technology. The dispensingrate of each head depends on the number of nozzles, the type of nozzlesand the applied voltage signal rate (frequency). Such dispensing headsare known to those skilled in the art of solid freeform fabrication.

Optionally, but not obligatorily, the overall number of dispensingnozzles or nozzle arrays is selected such that half of the dispensingnozzles are designated to dispense support material formulations andhalf of the dispensing nozzles are designated to dispense modelingmaterial formulations, i.e. the number of nozzles jetting modelingmaterials is the same as the number of nozzles jetting support material.Yet it is to be understood that it is not intended to limit the scope ofthe present invention and that the number of modeling materialdepositing heads (modeling heads) and the number of support materialdepositing heads (support heads) may differ. Generally, the number ofmodeling heads, the number of support heads and the number of nozzles ineach respective head or head array are selected such as to provide apredetermined ratio, a, between the maximal dispensing rate of thesupport material and the maximal dispensing rate of modeling material.The value of the predetermined ratio, a, is preferably selected toensure that in each formed layer, the height of modeling material equalsthe height of support material. Typical values for a are from about 0.6to about 1.5.

For example, for a=1, the overall dispensing rate of support materialformulation is generally the same as the overall dispensing rate of themodeling material formulation(s) when all modeling heads and supportheads operate.

In a preferred embodiment, there are M modeling heads each having marrays of p nozzles, and S support heads each having s arrays of qnozzles such that M×m×p=S×s×q. Each of the M×m modeling arrays and S×ssupport arrays can be manufactured as a separate physical unit, whichcan be assembled and disassembled from the group of arrays. In thisembodiment, each such array optionally and preferably comprises atemperature control unit and a material level sensor of its own, andreceives an individually controlled voltage for its operation.

The AM apparatus can further comprise a curing unit which can compriseone or more sources of a curing energy or a curing condition. The curingsource can be, for example, a radiation source, such as an ultravioletor visible or infrared lamp, or other sources of electromagneticradiation, or electron beam source, depending on the modeling materialformulation(s) being used. The curing energy source serves for curing orsolidifying the building material formulation(s).

The dispensing head and curing energy source (e.g., radiation source)source are preferably mounted in a frame or block which is preferablyoperative to reciprocally move over a tray, which serves as the workingsurface (a receiving medium). In some embodiments of the presentinvention, the curing energy (e.g., radiation) sources are mounted inthe block such that they follow in the wake of the dispensing heads toat least partially cure or solidify the materials just dispensed by thedispensing heads. According to the common conventions, the tray ispositioned in the X-Y plane, and is preferably configured to movevertically (along the Z direction), typically downward. In variousexemplary embodiments of the invention, the AM apparatus furthercomprises one or more leveling devices, e.g. a roller, which serve tostraighten, level and/or establish a thickness of the newly formed layerprior to the formation of the successive layer thereon. The levelingdevice preferably comprises a waste collection device for collecting theexcess material generated during leveling. The waste collection devicemay comprise any mechanism that delivers the material to a waste tank orwaste cartridge.

In use, the dispensing heads as described herein move in a scanningdirection, which is referred to herein as the X direction, andselectively dispense building material in a predetermined configurationin the course of their passage over the tray. The building materialtypically comprises one or more types of support material formulationsand one or more types of modeling material formulations. The passage ofthe dispensing heads is followed by the curing of the modeling andsupport material formulation(s) by the source of curing energy orcondition (e.g., radiation). In the reverse passage of the heads, backto their starting point for the layer just deposited, an additionaldispensing of building material may be carried out, according topredetermined configuration. In the forward and/or reverse passages ofthe dispensing heads, the layer thus formed may be straightened by theleveling device, which preferably follows the path of the dispensingheads in their forward and/or reverse movement. Once the dispensingheads return to their starting point along the X direction, they maymove to another position along an indexing direction, referred to hereinas the Y direction, and continue to build the same layer by reciprocalmovement along the X direction. Alternatively, the dispensing heads maymove in the Y direction between forward and reverse movements or aftermore than one forward-reverse movement. The series of scans performed bythe dispensing heads to complete a single layer is referred to herein asa single scan cycle.

Once the layer is completed, the tray is lowered in the Z direction to apredetermined Z level, according to the desired thickness of the layersubsequently to be printed. The procedure is repeated to form athree-dimensional object which comprises a modeling material and asupport material in a layerwise manner.

In some embodiments, the tray may be displaced in the Z directionbetween forward and reverse passages of the dispensing head, within thelayer. Such Z displacement is carried out in order to cause contact ofthe leveling device with the surface in one direction and preventcontact in the other direction.

The system for performing the method as described herein optionally andpreferably comprises a building material supply apparatus whichcomprises the building material containers or cartridges and supplies aplurality of building material formulations (modeling materialformulation(s) and a support material formulation as described herein tothe fabrication apparatus.

The system may further comprise a control unit which controls thefabrication apparatus and optionally and preferably also the supplyapparatus as described herein. The control unit preferably communicateswith a data processor which transmits digital data pertaining tofabrication instructions based on computer object data, stored on acomputer readable medium, preferably a non-transitory medium, in a formof a Standard Tessellation Language (STL) format or any other formatsuch as, but not limited to, the aforementioned formats. Typically, thecontrol unit controls the voltage applied to each dispensing head ornozzle array and the temperature of the building material in therespective printing head.

Once the manufacturing data is loaded to the control unit, it canoperate without user intervention. In some embodiments, the control unitreceives additional input from the operator, e.g., using a dataprocessor or using a user interface communicating with the control unit.The user interface can be of any type known in the art, such as, but notlimited to, a keyboard, a touch screen and the like. For example, thecontrol unit can receive, as additional input, one or more buildingmaterial types and/or attributes, such as, but not limited to, color,characteristic distortion and/or transition temperature, viscosity,electrical property, magnetic property. Other attributes and groups ofattributes are also contemplated.

Some embodiments contemplate the fabrication of an object by dispensingdifferent materials from different dispensing heads. These embodimentsprovide, inter alia, the ability to select materials from a given numberof materials and define desired combinations of the selected materialsand their properties. According to the present embodiments, the spatiallocations of the deposition of each material with the layer is defined,either to effect occupation of different three-dimensional spatiallocations by different materials, or to effect occupation ofsubstantially the same three-dimensional location or adjacentthree-dimensional locations by two or more different materials so as toallow post deposition spatial combination of the materials within thelayer, thereby to form a composite material at the respective locationor locations.

Any post deposition combination or mix of modeling materials iscontemplated. For example, once a certain material is dispensed it maypreserve its original properties. However, when it is dispensedsimultaneously with another modeling material or other dispensedmaterials which are dispensed at the same or nearby locations, acomposite material having a different property or properties to thedispensed materials is formed.

The present embodiments thus enable the deposition of a broad range ofmaterial combinations, and the fabrication of an object which mayconsist of multiple different combinations of materials, in differentparts of the object, according to the properties desired to characterizeeach part of the object.

Further details on the principles and operations of an AM system such asdescribed herein is found in U.S. patent application having PublicationNo. 2013/0073068, the contents of which are hereby incorporated byreference.

According to some embodiments of each of the methods and systemsdescribed herein, the uncured building material comprises at least onesupport material formulation as described herein.

The Model Object:

According to an aspect of some embodiments of the present invention,there is provided a three-dimension model object prepared by the methodas described herein, in any of the embodiments thereof and anycombination thereof.

According to an aspect of some embodiments of the present inventionthere is provided a 3D model object, fabricated by an AM method asdescribed herein.

As used herein the term “about” refers to ±10%.

The terms “comprises”, “comprising”, “includes”, “including”, “having”and their conjugates mean “including but not limited to”.

The term “consisting of” means “including and limited to”.

The term “consisting essentially of” means that the composition, methodor structure may include additional ingredients, steps and/or parts, butonly if the additional ingredients, steps and/or parts do not materiallyalter the basic and novel characteristics of the claimed composition,method or structure.

As used herein, the singular form “a”, “an” and “the” include pluralreferences unless the context clearly dictates otherwise. For example,the term “a compound” or “at least one compound” may include a pluralityof compounds, including mixtures thereof. Throughout this application,various embodiments of this invention may be presented in a rangeformat. It should be understood that the description in range format ismerely for convenience and brevity and should not be construed as aninflexible limitation on the scope of the invention. Accordingly, thedescription of a range should be considered to have specificallydisclosed all the possible subranges as well as individual numericalvalues within that range. For example, description of a range such asfrom 1 to 6 should be considered to have specifically disclosedsubranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4,from 2 to 6, from 3 to 6 etc., as well as individual numbers within thatrange, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of thebreadth of the range.

Whenever a numerical range is indicated herein, it is meant to includeany cited numeral (fractional or integral) within the indicated range.The phrases “ranging/ranges between” a first indicate number and asecond indicate number and “ranging/ranges from” a first indicate number“to” a second indicate number are used herein interchangeably and aremeant to include the first and second indicated numbers and all thefractional and integral numerals therebetween.

As used herein the term “method” refers to manners, means, techniquesand procedures for accomplishing a given task including, but not limitedto, those manners, means, techniques and procedures either known to, orreadily developed from known manners, means, techniques and proceduresby practitioners of the chemical, pharmacological, biological,biochemical and medical arts.

It is appreciated that certain features of the invention, which are, forclarity, described in the context of separate embodiments, may also beprovided in combination in a single embodiment. Conversely, variousfeatures of the invention, which are, for brevity, described in thecontext of a single embodiment, may also be provided separately or inany suitable subcombination or as suitable in any other describedembodiment of the invention. Certain features described in the contextof various embodiments are not to be considered essential features ofthose embodiments, unless the embodiment is inoperative without thoseelements.

Herein throughout, the phrase “linking moiety” or “linking group”describes a group that connects two or more moieties or groups in acompound. A linking moiety is typically derived from a bi- ortri-functional compound, and can be regarded as a bi- or tri-radicalmoiety, which is connected to two or three other moieties, via two orthree atoms thereof, respectively.

Exemplary linking moieties include a hydrocarbon moiety or chain,optionally interrupted by one or more heteroatoms, as defined herein,and/or any of the chemical groups listed below, when defined as linkinggroups.

When a chemical group is referred to herein as “end group” it is to beinterpreted as a substituent, which is connected to another group viaone atom thereof.

Herein throughout, the term “hydrocarbon” collectively describes achemical group composed mainly of carbon and hydrogen atoms. Ahydrocarbon can be comprised of alkyl, alkene, alkyne, aryl, and/orcycloalkyl, each can be substituted or unsubstituted, and can beinterrupted by one or more heteroatoms. The number of carbon atoms canrange from 2 to 20, and is preferably lower, e.g., from 1 to 10, or from1 to 6, or from 1 to 4. A hydrocarbon can be a linking group or an endgroup.

As used herein, the term “amine” describes both a —NRxRy group and a—NRx- group, wherein Rx and Ry are each independently hydrogen, alkyl,cycloalkyl, aryl, as these terms are defined hereinbelow.

The amine group can therefore be a primary amine, where both Rx and Ryare hydrogen, a secondary amine, where Rx is hydrogen and Ry is alkyl,cycloalkyl or aryl, or a tertiary amine, where each of Rx and Ry isindependently alkyl, cycloalkyl or aryl.

Alternatively, Rx and Ry can each independently be hydroxyalkyl,trihaloalkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroaryl,heteroalicyclic, amine, halide, sulfonate, sulfoxide, phosphonate,hydroxy, alkoxy, aryloxy, thiohydroxy, thioalkoxy, thioaryloxy, cyano,nitro, azo, sulfonamide, carbonyl, C-carboxylate, O-carboxylate,N-thiocarbamate, O-thiocarbamate, urea, thiourea, N-carbamate,O-carbamate, C-amide, N-amide, guanyl, guanidine and hydrazine.

The term “amine” is used herein to describe a —NRxRy group in caseswhere the amine is an end group, as defined hereinunder, and is usedherein to describe a —NRx- group in cases where the amine is a linkinggroup or is or part of a linking moiety.

The term “alkyl” describes a saturated aliphatic hydrocarbon includingstraight chain and branched chain groups. Preferably, the alkyl grouphas 1 to 20 carbon atoms. Whenever a numerical range; e.g., “1-20”, isstated herein, it implies that the group, in this case the alkyl group,may contain 1 carbon atom, 2 carbon atoms, 3 carbon atoms, etc., up toand including 20 carbon atoms. More preferably, the alkyl is a mediumsize alkyl having 1 to 10 carbon atoms. Most preferably, unlessotherwise indicated, the alkyl is a lower alkyl having 1 to 4 carbonatoms (C(1-4) alkyl). The alkyl group may be substituted orunsubstituted. Substituted alkyl may have one or more substituents,whereby each substituent group can independently be, for example,hydroxyalkyl, trihaloalkyl, cycloalkyl, alkenyl, alkynyl, aryl,heteroaryl, heteroalicyclic, amine, halide, sulfonate, sulfoxide,phosphonate, hydroxy, alkoxy, aryloxy, thiohydroxy, thioalkoxy,thioaryloxy, cyano, nitro, azo, sulfonamide, C-carboxylate,O-carboxylate, N-thiocarbamate, O-thiocarbamate, urea, thiourea,N-carbamate, O-carbamate, C-amide, N-amide, guanyl, guanidine andhydrazine.

The alkyl group can be an end group, as this phrase is definedhereinabove, wherein it is attached to a single adjacent atom, or alinking group, as this phrase is defined hereinabove, which connects twoor more moieties via at least two carbons in its chain. When the alkylis a linking group, it is also referred to herein as “alkylene” or“alkylene chain”.

Alkene and alkyne, as used herein, are an alkyl, as defined herein,which contains one or more double bond or triple bond, respectively.

The term “cycloalkyl” describes an all-carbon monocyclic ring or fusedrings (i.e., rings which share an adjacent pair of carbon atoms) groupwhere one or more of the rings does not have a completely conjugatedpi-electron system. Examples include, without limitation, cyclohexane,adamantine, norbornyl, isobornyl, and the like. The cycloalkyl group maybe substituted or unsubstituted. Substituted cycloalkyl may have one ormore substituents, whereby each substituent group can independently be,for example, hydroxyalkyl, trihaloalkyl, cycloalkyl, alkenyl, alkynyl,aryl, heteroaryl, heteroalicyclic, amine, halide, sulfonate, sulfoxide,phosphonate, hydroxy, alkoxy, aryloxy, thiohydroxy, thioalkoxy,thioaryloxy, cyano, nitro, azo, sulfonamide, C-carboxylate,O-carboxylate, N-thiocarbamate, O-thiocarbamate, urea, thiourea,N-carbamate, O-carbamate, C-amide, N-amide, guanyl, guanidine andhydrazine. The cycloalkyl group can be an end group, as this phrase isdefined hereinabove, wherein it is attached to a single adjacent atom,or a linking group, as this phrase is defined hereinabove, connectingtwo or more moieties at two or more positions thereof.

The term “heteroalicyclic” describes a monocyclic or fused ring grouphaving in the ring(s) one or more atoms such as nitrogen, oxygen andsulfur. The rings may also have one or more double bonds. However, therings do not have a completely conjugated pi-electron system.Representative examples are piperidine, piperazine, tetrahydrofuran,tetrahydropyrane, morpholino, oxalidine, and the like. Theheteroalicyclic may be substituted or unsubstituted. Substitutedheteroalicyclic may have one or more substituents, whereby eachsubstituent group can independently be, for example, hydroxyalkyl,trihaloalkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroaryl,heteroalicyclic, amine, halide, sulfonate, sulfoxide, phosphonate,hydroxy, alkoxy, aryloxy, thiohydroxy, thioalkoxy, thioaryloxy, cyano,nitro, azo, sulfonamide, C-carboxylate, O-carboxylate, N-thiocarbamate,O-thiocarbamate, urea, thiourea, O-carbamate, N-carbamate, C-amide,N-amide, guanyl, guanidine and hydrazine. The heteroalicyclic group canbe an end group, as this phrase is defined hereinabove, where it isattached to a single adjacent atom, or a linking group, as this phraseis defined hereinabove, connecting two or more moieties at two or morepositions thereof.

The term “aryl” describes an all-carbon monocyclic or fused-ringpolycyclic (i.e., rings which share adjacent pairs of carbon atoms)groups having a completely conjugated pi-electron system. The aryl groupmay be substituted or unsubstituted. Substituted aryl may have one ormore substituents, whereby each substituent group can independently be,for example, hydroxyalkyl, trihaloalkyl, cycloalkyl, alkenyl, alkynyl,aryl, heteroaryl, heteroalicyclic, amine, halide, sulfonate, sulfoxide,phosphonate, hydroxy, alkoxy, aryloxy, thiohydroxy, thioalkoxy,thioaryloxy, cyano, nitro, azo, sulfonamide, C-carboxylate,O-carboxylate, N-thiocarbamate, O-thiocarbamate, urea, thiourea,N-carbamate, O-carbamate, C-amide, N-amide, guanyl, guanidine andhydrazine. The aryl group can be an end group, as this term is definedhereinabove, wherein it is attached to a single adjacent atom, or alinking group, as this term is defined hereinabove, connecting two ormore moieties at two or more positions thereof.

The term “heteroaryl” describes a monocyclic or fused ring (i.e., ringswhich share an adjacent pair of atoms) group having in the ring(s) oneor more atoms, such as, for example, nitrogen, oxygen and sulfur and, inaddition, having a completely conjugated pi-electron system. Examples,without limitation, of heteroaryl groups include pyrrole, furan,thiophene, imidazole, oxazole, thiazole, pyrazole, pyridine, pyrimidine,quinoline, isoquinoline and purine. The heteroaryl group may besubstituted or unsubstituted. Substituted heteroaryl may have one ormore substituents, whereby each substituent group can independently be,for example, hydroxyalkyl, trihaloalkyl, cycloalkyl, alkenyl, alkynyl,aryl, heteroaryl, heteroalicyclic, amine, halide, sulfonate, sulfoxide,phosphonate, hydroxy, alkoxy, aryloxy, thiohydroxy, thioalkoxy,thioaryloxy, cyano, nitro, azo, sulfonamide, C-carboxylate,O-carboxylate, N-thiocarbamate, O-thiocarbamate, urea, thiourea,O-carbamate, N-carbamate, C-amide, N-amide, guanyl, guanidine andhydrazine. The heteroaryl group can be an end group, as this phrase isdefined hereinabove, where it is attached to a single adjacent atom, ora linking group, as this phrase is defined hereinabove, connecting twoor more moieties at two or more positions thereof. Representativeexamples are pyridine, pyrrole, oxazole, indole, purine and the like.

The term “halide” and “halo” describes fluorine, chlorine, bromine oriodine.

The term “haloalkyl” describes an alkyl group as defined above, furthersubstituted by one or more halide.

The term “sulfate” describes a —O—S(═O)₂—ORx end group, as this term isdefined hereinabove, or an —O—S(═O)₂—O— linking group, as these phrasesare defined hereinabove, where Rx is as defined hereinabove.

The term “thiosulfate” describes a —O—S(═S)(═O)—ORx end group or a—O—S(═S)(═O)—O— linking group, as these phrases are defined hereinabove,where Rx is as defined hereinabove.

The term “sulfite” describes an —O—S(═O)—O— Rx end group or a—O—S(═O)—O— group linking group, as these phrases are definedhereinabove, where Rx′ is as defined hereinabove.

The term “thiosulfite” describes a —O—S(═S)—O— Rx end group or an—O—S(═S)—O— group linking group, as these phrases are definedhereinabove, where Rx is as defined hereinabove.

The term “sulfinate” describes a —S(═O)—ORx end group or an —S(═O)—O—group linking group, as these phrases are defined hereinabove, where Rxis as defined hereinabove.

The term “sulfoxide” or “sulfinyl” describes a —S(═O)Rx end group or an—S(═O)— linking group, as these phrases are defined hereinabove, whereRx is as defined hereinabove.

The term “sulfonate” describes a —S(═O)₂—Rx end group or an —S(═O)₂—linking group, as these phrases are defined hereinabove, where Rx is asdefined herein.

The term “S-sulfonamide” describes a —S(═O)₂—NRxRy end group or a—S(═O)₂—NRx- linking group, as these phrases are defined hereinabove,with Rx and Ry as defined herein.

The term “N-sulfonamide” describes an RxS(═O)₂—NRy- end group or a—S(═O)₂—NRx- linking group, as these phrases are defined hereinabove,where Rx and Ry are as defined herein.

The term “disulfide” refers to a —S—SRx end group or a —S—S— linkinggroup, as these phrases are defined hereinabove, where Rx is as definedherein.

The term “phosphonate” describes a —P(═O)(ORx)(ORy) end group or a—P(═O)(ORx)(O)— linking group, as these phrases are defined hereinabove,with Rx and Ry as defined herein.

The term “thiophosphonate” describes a —P(═S)(ORx)(ORy) end group or a—P(═S)(ORx)(O)— linking group, as these phrases are defined hereinabove,with Rx and Ry as defined herein.

The term “phosphinyl” describes a —PRxRy end group or a —PRx- linkinggroup, as these phrases are defined hereinabove, with Rx and Ry asdefined hereinabove.

The term “phosphine oxide” describes a —P(═O)(Rx)(Ry) end group or a—P(═O)(Rx)- linking group, as these phrases are defined hereinabove,with Rx and Ry as defined herein.

The term “phosphine sulfide” describes a —P(═S)(Rx)(Ry) end group or a—P(═S)(Rx)- linking group, as these phrases are defined hereinabove,with Rx and Ry as defined herein.

The term “phosphite” describes an —O—PRx(═O)(ORy) end group or an—O—PRx(═O)(O)— linking group, as these phrases are defined hereinabove,with Rx and Ry as defined herein.

The term “carbonyl” or “carbonate” as used herein, describes a —C(═O)—Rxend group or a —C(═O)— linking group, as these phrases are definedhereinabove, with Rx as defined herein.

The term “thiocarbonyl” as used herein, describes a —C(═S)—Rx end groupor a —C(═S)— linking group, as these phrases are defined hereinabove,with Rx as defined herein.

The term “oxo” as used herein, describes a (═O) group, wherein an oxygenatom is linked by a double bond to the atom (e.g., carbon atom) at theindicated position.

The term “thiooxo” as used herein, describes a (═S) group, wherein asulfur atom is linked by a double bond to the atom (e.g., carbon atom)at the indicated position.

The term “oxime” describes a ═N—OH end group or a ═N—O— linking group,as these phrases are defined hereinabove.

The term “hydroxyl” describes a —OH group.

The term “alkoxy” describes both an —O-alkyl and an —O-cycloalkyl group,as defined herein.

The term “aryloxy” describes both an —O-aryl and an —O-heteroaryl group,as defined herein.

The term “thiohydroxy” describes a —SH group.

The term “thioalkoxy” describes both a —S-alkyl group, and a—S-cycloalkyl group, as defined herein.

The term “thioaryloxy” describes both a —S-aryl and a —S-heteroarylgroup, as defined herein.

The “hydroxyalkyl” is also referred to herein as “alcohol”, anddescribes an alkyl, as defined herein, substituted by a hydroxy group.

The term “cyano” describes a —C≡N group.

The term “isocyanate” describes an —N═C═O group.

The term “isothiocyanate” describes an —N═C═S group.

The term “nitro” describes an —NO₂ group.

The term “acyl halide” describes a —(C═O)Rz group wherein Rz is halide,as defined hereinabove.

The term “azo” or “diazo” describes an —N═NRx end group or an —N═N—linking group, as these phrases are defined hereinabove, with Rx asdefined hereinabove.

The term “peroxo” describes an —O—ORx end group or an —O—O— linkinggroup, as these phrases are defined hereinabove, with Rx as definedhereinabove.

The term “carboxylate” as used herein encompasses C-carboxylate and O—carboxylate.

The term “C-carboxylate” describes a —C(═O)—ORx end group or a—C(═O)—O—linking group, as these phrases are defined hereinabove, whereRx is as defined herein.

The term “O-carboxylate” describes a —OC(═O)Rx end group or a —OC(═O)—linking group, as these phrases are defined hereinabove, where Rx is asdefined herein.

A carboxylate can be linear or cyclic. When cyclic, Rx and the carbonatom are linked together to form a ring, in C-carboxylate, and thisgroup is also referred to as lactone. Alternatively, Rx and O are linkedtogether to form a ring in O-carboxylate. Cyclic carboxylates canfunction as a linking group, for example, when an atom in the formedring is linked to another group.

The term “thiocarboxylate” as used herein encompasses C-thiocarboxylateand O-thiocarboxylate.

The term “C-thiocarboxylate” describes a —C(═S)—ORx end group or a—C(═S)—O—linking group, as these phrases are defined hereinabove, whereRx is as defined herein.

The term “O-thiocarboxylate” describes a —OC(═S)Rx end group or a—OC(═S)— linking group, as these phrases are defined hereinabove, whereRx is as defined herein.

A thiocarboxylate can be linear or cyclic. When cyclic, Rx and thecarbon atom are linked together to form a ring, in C-thiocarboxylate,and this group is also referred to as thiolactone. Alternatively, Rx andO are linked together to form a ring in O-thiocarboxylate. Cyclicthiocarboxylates can function as a linking group, for example, when anatom in the formed ring is linked to another group.

The term “carbamate” as used herein encompasses N-carbamate andO-carbamate.

The term “N-carbamate” describes an RyOC(═O)—NRx- end group or a—OC(═O)—NRx- linking group, as these phrases are defined hereinabove,with Rx and Ry as defined herein.

The term “O-carbamate” describes an —OC(═O)—NRxRy end group or an—OC(═O)—NRx- linking group, as these phrases are defined hereinabove,with Rx and Ry as defined herein.

A carbamate can be linear or cyclic. When cyclic, Rx and the carbon atomare linked together to form a ring, in O-carbamate. Alternatively, Rxand O are linked together to form a ring in N-carbamate. Cycliccarbamates can function as a linking group, for example, when an atom inthe formed ring is linked to another group.

The term “carbamate” as used herein encompasses N-carbamate andO-carbamate.

The term “thiocarbamate” as used herein encompasses N-thiocarbamate andO-thiocarbamate.

The term “O-thiocarbamate” describes a —OC(═S)—NRxRy end group or a—OC(═S)—NRx- linking group, as these phrases are defined hereinabove,with Rx and Ry as defined herein.

The term “N-thiocarbamate” describes an RyOC(═S)NRx- end group or a—OC(═S)NRx- linking group, as these phrases are defined hereinabove,with Rx and Ry as defined herein.

Thiocarbamates can be linear or cyclic, as described herein forcarbamates.

The term “dithiocarbamate” as used herein encompasses S-dithiocarbamateand N-dithiocarbamate.

The term “S-dithiocarbamate” describes a —SC(═S)—NRxRy end group or a—SC(═S)NRx- linking group, as these phrases are defined hereinabove,with Rx and Ry as defined herein.

The term “N-dithiocarbamate” describes an RySC(═S)NRx- end group or a—SC(═S)NRx- linking group, as these phrases are defined hereinabove,with Rx and Ry as defined herein.

The term “urea”, which is also referred to herein as “ureido”, describesa —NRxC(═O)—NRyRq end group or a —NRxC(═O)—NRy- linking group, as thesephrases are defined hereinabove, where Rz and Ry are as defined hereinand Rq is as defined herein for Rx and Ry.

The term “thiourea”, which is also referred to herein as “thioureido”,describes a —NRx-C(═S)—NRyRq end group or a —NRx-C(═S)—NRy- linkinggroup, with Rx, Ry and Rq as defined herein.

The term “amide” as used herein encompasses C-amide and N-amide.

The term “C-amide” describes a —C(═O)—NRxRy end group or a—C(═O)—NRx-linking group, as these phrases are defined hereinabove,where Rx and Ry are as defined herein.

The term “N-amide” describes a RxC(═O)—NRy- end group or aRxC(═O)—N—linking group, as these phrases are defined hereinabove, whereRx and Ry are as defined herein.

An amide can be linear or cyclic. When cyclic, Rx and the carbon atomare linked together to form a ring, in C-amide, and this group is alsoreferred to as lactam. Cyclic amides can function as a linking group,for example, when an atom in the formed ring is linked to another group.

The term “guanyl” describes a RxRyNC(═N)— end group or a —RxNC(═N)—linking group, as these phrases are defined hereinabove, where Rx and Ryare as defined herein.

The term “guanidine” describes a —RxNC(═N)—NRyRq end group or a—RxNC(═N)—NRy- linking group, as these phrases are defined hereinabove,where Rx, Ry and Rq are as defined herein.

The term “hydrazine” describes a —NRx-NRyRq end group or a—NRx-NRy-linking group, as these phrases are defined hereinabove, withRx, Ry, and Rq as defined herein.

As used herein, the term “hydrazide” describes a —C(═O)—NRx-NRyRq endgroup or a —C(═O)—NRx-NRy- linking group, as these phrases are definedhereinabove, where Rx, Ry and Rq are as defined herein.

As used herein, the term “thiohydrazide” describes a —C(═S)—NRx-NRyRqend group or a —C(═S)—NRx-NRy- linking group, as these phrases aredefined hereinabove, where Rx, Ry and Rq are as defined herein.

As used herein, the term “alkylene glycol” describes a—O—[(CRxRy)_(z)-O]_(y)Rq end group or a —O—[(CRxRy)_(z)-O]_(y) linkinggroup, with Rx, Ry and Rq being as defined herein, and with z being aninteger of from 1 to 10, preferably, 2-6, more preferably 2 or 3, and ybeing an integer of 1 or more. Preferably Rx and Ry are both hydrogen.When z is 2 and y is 1, this group is ethylene glycol. When z is 3 and yis 1, this group is propylene glycol.

When y is greater than 4, the alkylene glycol is referred to herein aspoly(alkylene glycol). In some embodiments of the present invention, apoly(alkylene glycol) group or moiety can have from 10 to 200 repeatingalkylene glycol units, such that z is 10 to 200, preferably 10-100, morepreferably 10-50.

Various embodiments and aspects of the present invention as delineatedhereinabove and as claimed in the claims section below find experimentalsupport in the following examples.

EXAMPLES

Reference is now made to the following examples, which together with theabove descriptions illustrate some embodiments of the invention in a nonlimiting fashion.

Example 1

Exemplary commercially available materials usable in soluble supporttechnologies for AM processes such as 3D inkjet printing may comprisenon-curable (non-reactive) polymeric materials such as polyols (e.g.,glycols), and a mixture of mono-functional and di-functional curablemonomers or oligomers.

Exemplary mono-functional curable materials (curable monomers, oligomersor polymers) are poly(alkylene glycol) acrylates such as, but notlimited to, PEG monoacrylate reagents such as SR-256, SR-410 SR-550,marketed by SARTOMER company, PEG methacrylate reagents such as Bisomer®MPEG350MA, Bisomer® and PEM6 LD, marketed by GEO®), and PPG acrylatereagents such as Bisomer® PPA6 marketed by GEO.

These exemplary mono-functional materials can be collectivelyrepresented by the following general Formula IV:

wherein:

n is an integer ranging from 2 to 10, or from 2 to 8;

m is an integer ranging from 2 to 6, preferably from 2 to 4, or is 2 or3;

R′ can be hydrogen, alkyl, cycloalkyl, or aryl; and

Ra is H or C(1-4) alkyl.

Exemplary di-functional curable materials (curable monomers, oligomersor polymers) include di-functional poly(alkylene glycol) diacrylates,which can be represented by the following general Formula V:

wherein:

n is an integer ranging from 2 to 40, or from 2 to 20, or from 2 to 10,or from 2 to 8;

m is an integer ranging from 2 to 6, preferably from 2 to 4, or is 2 or3; and

Ra and Rb are each independently H or C(1-4) alkyl.

When a di-functional curable material is present in a support materialformulation, it may act as a chemical cross-linking agent whichcovalently links two or more polymeric chains formed upon curing thecurable materials. As a result, the cured support material comprisescross-linked polymeric chains, and hence a certain degree of chemicalcross-linking, depending on the concentration and type of thedi-functional curable material.

The presence of chemically cross-linked polymeric chains in a curedsupport material is assumed to provide the cured support material withthe desired mechanical strength, yet, it also adversely affects thedissolution of the cured support material in an aqueous solution.

For example, a support material formulation which comprises a mixture ofa poly(alkylene glycol) monoacrylate and a poly(alkylene glycol)diacrylate, as described herein, at a ratio that ranges, for example,from 70:30 to 95:5, by weight, at a total concentration of the curablemonomers of 35-40% by weight (e.g., 38.1% by weight), is non-soluble inwater and is typically dissolvable in a concentrated alkaline solution,for example a 5% NaOH solution, yet, the dissolution rate is relativelylow and a dissolution time is high. For example, a complete dissolutionof a 16-gram (20×20×20 mm) cube printed using such a support materialformulation immersed in a 800 mL of cleaning solution of 2% SodiumHydroxide and 1% Sodium Metasilicate, under continuous stirring, wasobserved after 11 hours. In addition, a saturation of the cleaningsolution is observed already when 5% by weight of a dissolved solublematerial are present in the solution.

In an attempt to increase the dissolution rate of support materialformulations comprising a mixture of mono-functional and di-functionalcurable monomers (e.g., acrylate monomers), as described herein, thepresent inventors have studied the effect of reducing the totalconcentration of the curable monomers in a soluble support formulation.

To this effect, three formulations, denoted herein F1, F2 and F3, wereprepared with varying total concentrations of a mixture ofmono-functional and di-functional poly(alkylene glycol) acrylatemonomers (hereinafter referred to as “poly(alkylene glycol) acrylatemixture”, as follows: F1—38.1% by weight poly(alkylene glycol) acrylatemixture; F2—26.7% by weight poly(alkylene glycol) acrylate mixture; andF3—21.7% by weight poly(alkylene glycol) acrylate mixture. The weightratio of the mono-functional acrylate to di-functional acrylate in eachof the formulations was about 90:10.

Each formulation contained, in addition to the poly(alkylene glycol)acrylate mixture at the above-indicated concentrations, a non-curablepolyol, at a concentration of 30-80 weight percents, a photoinitiator(e.g., of the BAPO type), at a concentration of 0.1-2 weight percents,an inhibitor at a concentration of 0.1-2 weight percents, and asurfactant, at a concentration of 0.1-2 weight percents.

A 16-gram (20 mm×20 mm×20 mm) cube printed (by 3D inkjet printing asdescribed herein) using such a support material formulation, and cured,was immersed in an 800 mL of a cleaning solution of 2% wt. SodiumHydroxide and 1% wt. Sodium Metasilicate. As shown in FIG. 1 , reducingthe concentration of the poly(alkylene glycol) acrylate mixture by about30% (from 38.1% wt. in F1 to 26.7% wt. in F2) resulted in about 2-folddecrease in the dissolution time, and decreasing the concentration ofthe poly(alkylene glycol) acrylate mixture by about 43% (from 38.1% wt.in F1 to 21.7% wt. in F3) resulted in more than 4.5-fold decrease in thedissolution time.

In order to determine the effect of reducing the concentration of thepoly(alkylene glycol) acrylate mixture in the support materialformulation, the mechanical strength of the objects printed from F1, F2and F3 was determined.

Mechanical strength was determined by compression tests performed usingLLOYD tensiometer model LR5K PLUS, operated at standard Compression setparameters, and is expressed by N, with respect to the above-mentionedcube.

The results are presented in FIG. 2 , and show a drastic decrease in themechanical strength of the cured support formulations as a result ofreducing the concentration of the poly(alkylene glycol) acrylatemixture. These results further show that 26.7% wt. of the poly(alkyleneglycol) acrylate mixture is the lowest limit of the poly(alkyleneglycol) acrylate mixture's concentration that provides a sufficientmechanical strength of the cured support material to support the modelin certain (e.g. PolyJet) 3D printing systems.

Without being bound by any particular theory, the present inventors haveassumed that the relatively high dissolution time of poly(alkyleneglycol) acrylate mixture-containing formulations is attributed tointermolecular interactions between the polymeric chains formed uponcuring the formulation, presumably chemical cross-linking effected by adi-functional acrylate monomer.

In a search for novel support material formulations that would exhibitimproved dissolution time without compromising the mechanical propertiesof the cured support material, the present inventors have conceivedreplacing at least a part of the monomers in the poly(alkylene glycol)acrylate mixture by a curable monomer that may interfere with theintermolecular interactions (e.g., chemical cross-linking) betweenpolymeric chains formed upon curing.

The present inventors have conceived that such a curable monomer shouldbe capable of forming polymeric chains that interact with otherpolymeric chains in the cured support material via non-covalentinteractions, for example, via hydrogen bonds. Thus, such a curablemonomer should exhibit at least two chemical moieties that canparticipate in hydrogen bond interactions, as this term is definedherein. Such chemical moieties are also referred to herein as“hydrogen-bond forming chemical moieties”.

The present inventors have therefore designed a novel formulation,termed herein “F4”, which comprises 16.7% wt. of the poly(alkyleneglycol) acrylate mixture and 10% wt. a water-soluble acryl amide thatfeatures one hydrogen-bond forming chemical moiety by means of the amidegroup, and an additional bond-forming chemical moiety, by means of asubstituent of the amide, whereby all other ingredients are the same asin formulations F1, F2 and F3.

An exemplary such an acrylamide compound can be presented by thefollowing formula I:

wherein Ra is hydrogen or C(1-4) alkyl;k is an integer of from 2-10, or from 2-8, or from 2-6, or from 2-4, oris 2 or 3; andY is a hydrogen bond-forming chemical moiety, for example, a moiety thatcontains oxygen or nitrogen (e.g., hydroxyl, amine, alkylamine, dialkylamine, and the like), as described herein.

As shown in FIG. 1 , the dissolution time of a cured support materialprinted with exemplary formulation F4, compared to F2, decreaseddrastically, by more than 3-folds.

Surprisingly, as shown in FIG. 2 , the mechanical strength of the curedsupport material was almost 3-folds higher for F4, compared to F2, andwas in line with the requirements of a support material in (e.g.,PolyJet) 3D printing systems. The improved dissolution time exhibited bythe F4 formulation was demonstrated in further studies.

Formulations F1, F2, F3 and F4 were used to print various shapes,namely, Brain Gear (BG), Lego and Small Flute. Upon curing, the printedobjects were subjected to dissolution by a 5% NaOH solution, in a Jigcleaning system.

The results are presented in FIG. 3 . It can be seen that reducing theconcentration of the poly(alkylene glycol) acrylate mixture from 38.1%wt. (F1) to 26.7% wt. (F2), the dissolution time decreased by 2-foldsfor BG and Lego parts. By decreasing the concentration of thepoly(alkylene glycol) acrylate mixture below 26.7% wt. and adding theacrylamide monomer to a total monomer concentration of 26.7% wt. of thepoly(alkylene glycol) acrylate mixture and the additional acrylamidemonomer (F4) the dissolution time decreased by about 4-folds compared toF1, for the Lego part, and by about 10-folds for the BG part, comparedto F1.

In addition, the cured support material prepared from the F4 formulationwas shown to be soft enough to allow mechanical breakability, such thata substantial amount of the cured support material can be readilyremoved by mild mechanical means, and may circumvent the need to usechemical dissolution.

In additional experiments, a mixture of two acrylamide monomers thatfeature one hydrogen bond-forming chemical moiety as the amide and onehydrogen bond-forming chemical moiety as a substituent of the amide, wastested.

In these experiments, an acrylamide monomer as described herein, thatfeatures a relatively high Tg (e.g., higher than 120° C., or higher than130° C., e.g., 135° C.) was added to the support material formulation.

The additional acrylamide monomer was selected as such that forms arigid, hard, thermal-resistant, water-soluble solid polymer thatexhibits a dissolution time in water which is much lower than thedissolution time of other High Tg-monomers.

Formulation F5 contains 16.7% wt. of the poly(alkylene glycol) acrylatemixture, 5% wt. of an acrylamide monomer used in F4 and 5% wt. anadditional acrylamide monomer featuring high Tg and low dissolution timein water, with all other ingredients being the same as in F1-F4.Dissolution time and mechanical strength were determined as describedfor F1-F4 (FIGS. 1 and 2 ) in Example 1 hereinabove.

As shown in FIG. 4 , the dissolution time of a cured support materialprinted from formulation F5 was 2-folds lower than that of F4.

As shown in FIG. 5 , the mechanical strength of the cured supportmaterial increased by about 50%, compared to F4.

In order to verify that the hydrogen bond formation attributed to testedacrylamide compounds described above indeed accounts for the improvedperformance of support material formulations containing same, aformulation containing isobornyl acrylate (IBOA) was tested.

IBOA is a high Tg-monomer that does not feature two groups that arecapable of forming hydrogen bonds.

30 grams of the F4 formulation as described herein and 30 grams of asimilar formulation in which the acrylamide monomer was replaced by anequivalent amount of IBOA, were put in mold and cured in a UV oven for 5hours.

The mechanical strength of each of the cured formulations was measuredin LLOYD Tensiometer (compression set), as described herein.

The obtained data is presented in FIG. 6 and clearly shows thesubstantially higher mechanical strength was exhibited by the F4formulation.

Although the invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, it is intended to embrace all such alternatives,modifications and variations that fall within the spirit and broad scopeof the appended claims.

It is the intent of the applicant(s) that all publications, patents andpatent applications referred to in this specification are to beincorporated in their entirety by reference into the specification, asif each individual publication, patent or patent application wasspecifically and individually noted when referenced that it is to beincorporated herein by reference. In addition, citation oridentification of any reference in this application shall not beconstrued as an admission that such reference is available as prior artto the present invention. To the extent that section headings are used,they should not be construed as necessarily limiting. In addition, anypriority document(s) of this application is/are hereby incorporatedherein by reference in its/their entirety.

What is claimed is:
 1. A support material formulation comprising: anon-curable water-miscible polymer, in an amount that ranges from 30 to80 weight percent of the total weight of the formulation, saidnon-curable water-miscible polymer comprising an alkoxylated polyol; anon-curable water-miscible non-polymeric material which comprises1,2-propanediol; a first water-miscible, curable material in an amountthat ranges from 10 to 20 weight percent of the total weight of theformulation; and at least one second water-miscible curable material inan amount that ranges from 5 to 15 weight percent of the total weight ofthe formulation, wherein said first water-miscible curable materialcomprises a mono-functional poly(alkylene glycol) acrylate; and whereinsaid second water-miscible curable material is represented by Formula I:

wherein: Ra is selected from H, C(1-4) alkyl and a hydrophilic group; kis an integer ranging from 2 to 10; X is —NRc—, wherein Rc is hydrogen,alkyl, cycloalkyl or aryl; and Y is a hydrogen bond-forming moiety thatcomprises at least one nitrogen and/or oxygen atom, the formulationbeing devoid of a multi-functional curable material.
 2. The formulationof claim 1, wherein said second water-miscible curable material is anacrylamide substituted by said hydrogen bond-forming moiety.
 3. Theformulation of claim 1, wherein Y is selected from hydroxyl, alkoxy,aryloxy, amine, alkylamine, dialkylamine, carboxylate, hydrazine,carbamate, hydrazine, a nitrogen-containing heteralicyclic, and anoxygen-containing heteralicyclic.
 4. The formulation of claim 3, whereinX is —O—.
 5. The formulation of claim 4, wherein Ra is H, such that thesecond curable material is an acrylate.
 6. The formulation of claim 1,wherein Ra is H, such that the second curable material is an acrylamide.7. The formulation of claim 1, wherein said water-miscible polymercomprises said alkoxylated polyol and a polyethylene glycol.
 8. Theformulation of claim 1, wherein a concentration of said secondwater-miscible curable material ranges from 5 to 10 weight percent ofthe total weight of the formulation.
 9. The formulation of claim 1,further comprising an initiator, a surface active agent and/or aninhibitor.
 10. The formulation of claim 1, wherein each of said firstand second water-miscible curable materials is a UV-curable material.11. The formulation of claim 1, wherein a cured support material formedupon exposing the formulation to a curing energy is dissolvable in analkaline solution.
 12. The formulation of claim 11, wherein adissolution time of a cured support material when immersed in saidalkaline solution is at least 2-folds, or at least 4-folds, shorter thana dissolution time of a cured support material made of a comparablesupport material formulation that is absent said second water-misciblecurable material.
 13. The formulation of claim 11, wherein a dissolutiontime of a 16-grams cube made of said cured support material and immersedin 800 ml of said alkaline solution is less than 2 hours.
 14. Theformulation of claim 1, wherein a cured support material formed uponexposing the formulation to a curing energy is characterized by amechanical strength that is lower than a mechanical strength of a curedsupport material made of a comparable support material formulation thatis absent said second water-miscible curable material and comprisessubstantially the same total concentration of curable materials as theformulation, by no more than 50% or by no more than 40%, or by no morethan 30%.